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	$88.33	9.548%	$96.7637	$96.76	$96.75	$96.80
Purchase #2	$244.63	11.148%	$271.9014	$271.90	$271.90	$271.90
Purchase #3	$103.82	3.182%	$107.1236	$107.12	$107.10	$107.10
Purchase #4	$144.54	5.239%	$152.1125	$152.11	$152.10	$152.10
Purchase #5	$235.56	11.434%	$262.4939	$262.49	$262.50	$262.50
Purchase #6	$166.63	7.355%	$178.8856	$178.89	$178.90	$178.90
Purchase #7	$224.79	6.230%	$238.7944	$238.79	$238.80	$238.80
7 purchase totals =	$1,208.30		$1,308.0751	$1,308.06	$1,308.05	$1,308.10