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	$51.76	3.844%	$53.7497	$53.75	$53.75	$53.70
Purchase #2	$215.27	3.807%	$223.4653	$223.47	$223.45	$223.50
Purchase #3	$7.69	4.432%	$8.0308	$8.03	$8.05	$8.00
Purchase #4	$72.36	8.638%	$78.6105	$78.61	$78.60	$78.60
Purchase #5	$210.38	11.102%	$233.7364	$233.74	$233.75	$233.70
Purchase #6	$152.68	8.145%	$165.1158	$165.12	$165.10	$165.10
Purchase #7	$28.60	12.330%	$32.1264	$32.13	$32.15	$32.10
7 purchase totals =	$738.74		$794.8349	$794.85	$794.85	$794.70