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	$202.37	11.494%	$225.6304	$225.63	$225.65	$225.60
Purchase #2	$69.66	12.836%	$78.6016	$78.60	$78.60	$78.60
Purchase #3	$84.56	5.662%	$89.3478	$89.35	$89.35	$89.30
Purchase #4	$90.27	9.826%	$99.1399	$99.14	$99.15	$99.10
Purchase #5	$33.69	4.207%	$35.1073	$35.11	$35.10	$35.10
Purchase #6	$25.88	5.171%	$27.2183	$27.22	$27.20	$27.20
Purchase #7	$234.62	5.124%	$246.6419	$246.64	$246.65	$246.60
7 purchase totals =	$741.05		$801.6872	$801.69	$801.70	$801.50