Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$186.53	4.701%	$195.2988	$195.30	$195.30	$195.30
Purchase #2	$137.29	9.757%	$150.6854	$150.69	$150.70	$150.70
Purchase #3	$249.75	10.327%	$275.5417	$275.54	$275.55	$275.50
Purchase #4	$105.55	12.607%	$118.8567	$118.86	$118.85	$118.90
Purchase #5	$219.79	7.275%	$235.7797	$235.78	$235.80	$235.80
Purchase #6	$119.83	10.806%	$132.7788	$132.78	$132.80	$132.80
Purchase #7	$162.56	6.366%	$172.9086	$172.91	$172.90	$172.90
7 purchase totals =	$1,181.30		$1,281.8497	$1,281.86	$1,281.90	$1,281.90