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	$234.52	8.331%	$254.0579	$254.06	$254.05	$254.10
Purchase #2	$145.29	5.594%	$153.4175	$153.42	$153.40	$153.40
Purchase #3	$249.38	11.815%	$278.8442	$278.84	$278.85	$278.80
Purchase #4	$86.82	4.541%	$90.7625	$90.76	$90.75	$90.80
Purchase #5	$201.70	11.507%	$224.9096	$224.91	$224.90	$224.90
Purchase #6	$141.54	10.260%	$156.062	$156.06	$156.05	$156.10
Purchase #7	$127.32	10.466%	$140.6453	$140.65	$140.65	$140.60
7 purchase totals =	$1,186.57		$1,298.6990	$1,298.70	$1,298.65	$1,298.70