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	$48.94	10.114%	$53.8898	$53.89	$53.90	$53.90
Purchase #2	$113.70	9.448%	$124.4424	$124.44	$124.45	$124.40
Purchase #3	$58.79	4.665%	$61.5326	$61.53	$61.55	$61.50
Purchase #4	$70.59	4.595%	$73.8336	$73.83	$73.85	$73.80
Purchase #5	$175.59	12.834%	$198.1252	$198.13	$198.15	$198.10
Purchase #6	$218.85	11.597%	$244.23	$244.23	$244.25	$244.20
Purchase #7	$70.85	4.620%	$74.1233	$74.12	$74.10	$74.10
7 purchase totals =	$757.31		$830.1769	$830.17	$830.25	$830.00