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	$145.85	10.538%	$161.2197	$161.22	$161.20	$161.20
Purchase #2	$87.48	10.499%	$96.6645	$96.66	$96.65	$96.70
Purchase #3	$223.33	6.852%	$238.6326	$238.63	$238.65	$238.60
Purchase #4	$54.37	4.123%	$56.6117	$56.61	$56.60	$56.60
Purchase #5	$119.37	6.653%	$127.3117	$127.31	$127.30	$127.30
Purchase #6	$191.88	12.368%	$215.6117	$215.61	$215.60	$215.60
Purchase #7	$139.89	7.307%	$150.1118	$150.11	$150.10	$150.10
7 purchase totals =	$962.17		$1,046.1637	$1,046.15	$1,046.10	$1,046.10