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	$56.85	4.688%	$59.5151	$59.52	$59.50	$59.50
Purchase #2	$33.63	6.740%	$35.8967	$35.90	$35.90	$35.90
Purchase #3	$72.98	3.155%	$75.2825	$75.28	$75.30	$75.30
Purchase #4	$54.54	4.779%	$57.1465	$57.15	$57.15	$57.10
Purchase #5	$144.87	9.519%	$158.6602	$158.66	$158.65	$158.70
Purchase #6	$168.61	7.856%	$181.856	$181.86	$181.85	$181.90
Purchase #7	$121.82	4.394%	$127.1728	$127.17	$127.15	$127.20
7 purchase totals =	$653.30		$695.5298	$695.54	$695.50	$695.60