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	$84.37	4.633%	$88.2789	$88.28	$88.30	$88.30
Purchase #2	$195.31	6.644%	$208.2864	$208.29	$208.30	$208.30
Purchase #3	$74.84	13.670%	$85.0706	$85.07	$85.05	$85.10
Purchase #4	$144.56	6.611%	$154.1169	$154.12	$154.10	$154.10
Purchase #5	$188.74	10.612%	$208.7691	$208.77	$208.75	$208.80
Purchase #6	$28.70	12.568%	$32.307	$32.31	$32.30	$32.30
Purchase #7	$225.61	6.429%	$240.1145	$240.11	$240.10	$240.10
7 purchase totals =	$942.13		$1,016.9434	$1,016.95	$1,016.90	$1,017.00