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	$97.36	8.399%	$105.5373	$105.54	$105.55	$105.50
Purchase #2	$139.87	5.571%	$147.6622	$147.66	$147.65	$147.70
Purchase #3	$129.61	9.398%	$141.7907	$141.79	$141.80	$141.80
Purchase #4	$93.57	6.382%	$99.5416	$99.54	$99.55	$99.50
Purchase #5	$125.79	4.507%	$131.4594	$131.46	$131.45	$131.50
Purchase #6	$42.68	8.134%	$46.1516	$46.15	$46.15	$46.20
Purchase #7	$167.47	3.744%	$173.7401	$173.74	$173.75	$173.70
7 purchase totals =	$796.35		$845.8829	$845.88	$845.90	$845.90