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	$111.93	13.538%	$127.0831	$127.08	$127.10	$127.10
Purchase #2	$154.67	4.862%	$162.1901	$162.19	$162.20	$162.20
Purchase #3	$62.26	6.212%	$66.1276	$66.13	$66.15	$66.10
Purchase #4	$53.30	8.179%	$57.6594	$57.66	$57.65	$57.70
Purchase #5	$71.69	11.610%	$80.0132	$80.01	$80.00	$80.00
Purchase #6	$245.76	7.686%	$264.6491	$264.65	$264.65	$264.60
Purchase #7	$60.99	10.782%	$67.5659	$67.57	$67.55	$67.60
7 purchase totals =	$760.60		$825.2884	$825.29	$825.30	$825.30