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	$222.49	7.269%	$238.6628	$238.66	$238.65	$238.70
Purchase #2	$181.69	12.488%	$204.3794	$204.38	$204.40	$204.40
Purchase #3	$54.41	5.357%	$57.3247	$57.32	$57.30	$57.30
Purchase #4	$108.68	8.719%	$118.1558	$118.16	$118.15	$118.20
Purchase #5	$186.76	5.422%	$196.8861	$196.89	$196.90	$196.90
Purchase #6	$17.82	5.339%	$18.7714	$18.77	$18.75	$18.80
Purchase #7	$35.33	6.336%	$37.5685	$37.57	$37.55	$37.60
7 purchase totals =	$807.18		$871.7487	$871.75	$871.70	$871.90