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	$154.97	9.281%	$169.3528	$169.35	$169.35	$169.40
Purchase #2	$195.55	13.870%	$222.6728	$222.67	$222.65	$222.70
Purchase #3	$152.76	7.433%	$164.1147	$164.11	$164.10	$164.10
Purchase #4	$235.86	12.398%	$265.1019	$265.10	$265.10	$265.10
Purchase #5	$219.71	6.148%	$233.2178	$233.22	$233.20	$233.20
Purchase #6	$40.92	4.413%	$42.7258	$42.73	$42.75	$42.70
Purchase #7	$78.39	9.434%	$85.7853	$85.79	$85.80	$85.80
7 purchase totals =	$1,078.16		$1,182.9711	$1,182.97	$1,182.95	$1,183.00