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	$71.37	7.279%	$76.565	$76.57	$76.55	$76.60
Purchase #2	$40.62	8.244%	$43.9687	$43.97	$43.95	$44.00
Purchase #3	$105.32	3.328%	$108.825	$108.83	$108.85	$108.80
Purchase #4	$57.88	5.484%	$61.0541	$61.05	$61.05	$61.10
Purchase #5	$88.59	11.470%	$98.7513	$98.75	$98.75	$98.80
Purchase #6	$45.89	3.311%	$47.4094	$47.41	$47.40	$47.40
Purchase #7	$18.63	11.331%	$20.741	$20.74	$20.75	$20.70
7 purchase totals =	$428.30		$457.3145	$457.32	$457.30	$457.40