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	$127.73	10.465%	$141.0969	$141.10	$141.10	$141.10
Purchase #2	$125.45	4.543%	$131.1492	$131.15	$131.15	$131.10
Purchase #3	$160.78	4.128%	$167.417	$167.42	$167.40	$167.40
Purchase #4	$33.88	8.280%	$36.6853	$36.69	$36.70	$36.70
Purchase #5	$119.87	5.486%	$126.4461	$126.45	$126.45	$126.40
Purchase #6	$52.39	10.531%	$57.9072	$57.91	$57.90	$57.90
Purchase #7	$129.57	7.848%	$139.7387	$139.74	$139.75	$139.70
7 purchase totals =	$749.67		$800.4404	$800.46	$800.45	$800.30