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	$140.80	4.367%	$146.9487	$146.95	$146.95	$146.90
Purchase #2	$93.74	10.853%	$103.9136	$103.91	$103.90	$103.90
Purchase #3	$50.72	3.391%	$52.4399	$52.44	$52.45	$52.40
Purchase #4	$68.72	3.488%	$71.117	$71.12	$71.10	$71.10
Purchase #5	$167.96	11.840%	$187.8465	$187.85	$187.85	$187.80
Purchase #6	$50.67	12.790%	$57.1507	$57.15	$57.15	$57.20
Purchase #7	$57.73	8.173%	$62.4483	$62.45	$62.45	$62.40
7 purchase totals =	$630.34		$681.8647	$681.87	$681.85	$681.70