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	$153.53	9.351%	$167.8866	$167.89	$167.90	$167.90
Purchase #2	$249.74	9.592%	$273.6951	$273.70	$273.70	$273.70
Purchase #3	$142.93	10.829%	$158.4079	$158.41	$158.40	$158.40
Purchase #4	$188.91	3.454%	$195.435	$195.44	$195.45	$195.40
Purchase #5	$239.47	3.742%	$248.431	$248.43	$248.45	$248.40
Purchase #6	$161.94	7.414%	$173.9462	$173.95	$173.95	$173.90
Purchase #7	$75.71	9.452%	$82.8661	$82.87	$82.85	$82.90
7 purchase totals =	$1,212.23		$1,300.6679	$1,300.69	$1,300.70	$1,300.60