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	$233.39	8.422%	$253.0461	$253.05	$253.05	$253.00
Purchase #2	$102.29	8.600%	$111.0869	$111.09	$111.10	$111.10
Purchase #3	$6.37	11.365%	$7.094	$7.09	$7.10	$7.10
Purchase #4	$248.88	10.618%	$275.3061	$275.31	$275.30	$275.30
Purchase #5	$223.56	9.637%	$245.1045	$245.10	$245.10	$245.10
Purchase #6	$78.28	8.604%	$85.0152	$85.02	$85.00	$85.00
Purchase #7	$51.40	4.547%	$53.7372	$53.74	$53.75	$53.70
7 purchase totals =	$944.17		$1,030.3900	$1,030.40	$1,030.40	$1,030.30