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	$106.73	4.573%	$111.6108	$111.61	$111.60	$111.60
Purchase #2	$109.69	11.443%	$122.2418	$122.24	$122.25	$122.20
Purchase #3	$201.26	8.653%	$218.675	$218.68	$218.70	$218.70
Purchase #4	$176.48	7.735%	$190.1307	$190.13	$190.15	$190.10
Purchase #5	$174.39	4.270%	$181.8365	$181.84	$181.85	$181.80
Purchase #6	$94.30	6.762%	$100.6766	$100.68	$100.70	$100.70
Purchase #7	$152.37	4.421%	$159.1063	$159.11	$159.10	$159.10
7 purchase totals =	$1,015.22		$1,084.2777	$1,084.29	$1,084.35	$1,084.20