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	$169.57	9.171%	$185.1213	$185.12	$185.10	$185.10
Purchase #2	$44.97	13.194%	$50.9033	$50.90	$50.90	$50.90
Purchase #3	$116.35	7.640%	$125.2391	$125.24	$125.25	$125.20
Purchase #4	$170.64	3.337%	$176.3343	$176.33	$176.35	$176.30
Purchase #5	$204.88	10.608%	$226.6137	$226.61	$226.60	$226.60
Purchase #6	$165.57	11.872%	$185.2265	$185.23	$185.25	$185.20
Purchase #7	$50.91	10.256%	$56.1313	$56.13	$56.15	$56.10
7 purchase totals =	$922.89		$1,005.5695	$1,005.56	$1,005.60	$1,005.40