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	$167.50	6.124%	$177.7577	$177.76	$177.75	$177.80
Purchase #2	$92.60	13.315%	$104.9297	$104.93	$104.95	$104.90
Purchase #3	$104.33	8.110%	$112.7912	$112.79	$112.80	$112.80
Purchase #4	$80.84	10.740%	$89.5222	$89.52	$89.50	$89.50
Purchase #5	$196.83	11.842%	$220.1386	$220.14	$220.15	$220.10
Purchase #6	$181.70	5.383%	$191.4809	$191.48	$191.50	$191.50
Purchase #7	$220.86	11.315%	$245.8503	$245.85	$245.85	$245.90
7 purchase totals =	$1,044.66		$1,142.4706	$1,142.47	$1,142.50	$1,142.50