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	$235.39	6.827%	$251.4601	$251.46	$251.45	$251.50
Purchase #2	$188.41	4.364%	$196.6322	$196.63	$196.65	$196.60
Purchase #3	$79.62	3.492%	$82.4003	$82.40	$82.40	$82.40
Purchase #4	$147.72	7.769%	$159.1964	$159.20	$159.20	$159.20
Purchase #5	$40.72	6.251%	$43.2654	$43.27	$43.25	$43.30
Purchase #6	$110.98	12.534%	$124.8902	$124.89	$124.90	$124.90
Purchase #7	$97.53	10.489%	$107.7599	$107.76	$107.75	$107.80
7 purchase totals =	$900.37		$965.6045	$965.61	$965.60	$965.70