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	$69.66	3.148%	$71.8529	$71.85	$71.85	$71.90
Purchase #2	$191.69	12.578%	$215.8008	$215.80	$215.80	$215.80
Purchase #3	$92.94	11.757%	$103.867	$103.87	$103.85	$103.90
Purchase #4	$166.86	5.418%	$175.9005	$175.90	$175.90	$175.90
Purchase #5	$57.82	11.625%	$64.5416	$64.54	$64.55	$64.50
Purchase #6	$141.56	7.521%	$152.2067	$152.21	$152.20	$152.20
Purchase #7	$54.94	6.588%	$58.5594	$58.56	$58.55	$58.60
7 purchase totals =	$775.47		$842.7289	$842.73	$842.70	$842.80