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	$217.37	8.362%	$235.5465	$235.55	$235.55	$235.50
Purchase #2	$242.92	8.848%	$264.4136	$264.41	$264.40	$264.40
Purchase #3	$79.44	11.335%	$88.4445	$88.44	$88.45	$88.40
Purchase #4	$91.33	10.288%	$100.726	$100.73	$100.75	$100.70
Purchase #5	$52.68	9.232%	$57.5434	$57.54	$57.55	$57.50
Purchase #6	$242.78	5.451%	$256.0139	$256.01	$256.00	$256.00
Purchase #7	$167.59	10.652%	$185.4417	$185.44	$185.45	$185.40
7 purchase totals =	$1,094.11		$1,188.1296	$1,188.12	$1,188.15	$1,187.90