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	$176.98	7.689%	$190.588	$190.59	$190.60	$190.60
Purchase #2	$120.54	3.737%	$125.0446	$125.04	$125.05	$125.00
Purchase #3	$57.46	11.573%	$64.1098	$64.11	$64.10	$64.10
Purchase #4	$94.84	3.551%	$98.2078	$98.21	$98.20	$98.20
Purchase #5	$249.44	10.264%	$275.0425	$275.04	$275.05	$275.00
Purchase #6	$146.72	12.809%	$165.5134	$165.51	$165.50	$165.50
Purchase #7	$90.31	11.237%	$100.4581	$100.46	$100.45	$100.50
7 purchase totals =	$936.29		$1,018.9642	$1,018.96	$1,018.95	$1,018.90