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	$134.58	8.655%	$146.2279	$146.23	$146.25	$146.20
Purchase #2	$71.28	10.199%	$78.5498	$78.55	$78.55	$78.50
Purchase #3	$166.91	6.152%	$177.1783	$177.18	$177.20	$177.20
Purchase #4	$153.89	9.722%	$168.8512	$168.85	$168.85	$168.90
Purchase #5	$165.59	5.814%	$175.2174	$175.22	$175.20	$175.20
Purchase #6	$176.61	7.687%	$190.186	$190.19	$190.20	$190.20
Purchase #7	$152.87	9.618%	$167.573	$167.57	$167.55	$167.60
7 purchase totals =	$1,021.73		$1,103.7836	$1,103.79	$1,103.80	$1,103.80