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	$71.76	7.471%	$77.1212	$77.12	$77.10	$77.10
Purchase #2	$211.57	5.680%	$223.5872	$223.59	$223.60	$223.60
Purchase #3	$127.93	11.174%	$142.2249	$142.22	$142.20	$142.20
Purchase #4	$223.54	13.328%	$253.3334	$253.33	$253.35	$253.30
Purchase #5	$226.72	10.275%	$250.0155	$250.02	$250.00	$250.00
Purchase #6	$101.71	3.704%	$105.4773	$105.48	$105.50	$105.50
Purchase #7	$196.92	7.136%	$210.9722	$210.97	$210.95	$211.00
7 purchase totals =	$1,160.15		$1,262.7317	$1,262.73	$1,262.70	$1,262.70