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	$146.50	9.551%	$160.4922	$160.49	$160.50	$160.50
Purchase #2	$193.53	8.566%	$210.1078	$210.11	$210.10	$210.10
Purchase #3	$89.49	6.781%	$95.5583	$95.56	$95.55	$95.60
Purchase #4	$245.39	10.528%	$271.2247	$271.22	$271.20	$271.20
Purchase #5	$27.33	3.719%	$28.3464	$28.35	$28.35	$28.30
Purchase #6	$154.34	8.748%	$167.8417	$167.84	$167.85	$167.80
Purchase #7	$139.81	3.661%	$144.9284	$144.93	$144.95	$144.90
7 purchase totals =	$996.39		$1,078.4995	$1,078.50	$1,078.50	$1,078.40