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	$158.87	13.261%	$179.9378	$179.94	$179.95	$179.90
Purchase #2	$64.40	4.668%	$67.4062	$67.41	$67.40	$67.40
Purchase #3	$76.36	3.148%	$78.7638	$78.76	$78.75	$78.80
Purchase #4	$177.26	5.437%	$186.8976	$186.90	$186.90	$186.90
Purchase #5	$28.63	12.441%	$32.1919	$32.19	$32.20	$32.20
Purchase #6	$175.79	5.361%	$185.2141	$185.21	$185.20	$185.20
Purchase #7	$159.49	3.732%	$165.4422	$165.44	$165.45	$165.40
7 purchase totals =	$840.80		$895.8536	$895.85	$895.85	$895.80