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	$159.90	9.465%	$175.0345	$175.03	$175.05	$175.00
Purchase #2	$51.62	9.150%	$56.3432	$56.34	$56.35	$56.30
Purchase #3	$166.66	4.331%	$173.878	$173.88	$173.90	$173.90
Purchase #4	$67.66	7.227%	$72.5498	$72.55	$72.55	$72.50
Purchase #5	$233.54	7.496%	$251.0462	$251.05	$251.05	$251.00
Purchase #6	$152.72	12.151%	$171.277	$171.28	$171.30	$171.30
Purchase #7	$156.79	5.692%	$165.7145	$165.71	$165.70	$165.70
7 purchase totals =	$988.89		$1,065.8432	$1,065.84	$1,065.90	$1,065.70