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	$162.34	7.842%	$175.0707	$175.07	$175.05	$175.10
Purchase #2	$191.55	6.493%	$203.9873	$203.99	$204.00	$204.00
Purchase #3	$90.45	9.519%	$99.0599	$99.06	$99.05	$99.10
Purchase #4	$131.99	7.158%	$141.4378	$141.44	$141.45	$141.40
Purchase #5	$39.27	9.271%	$42.9107	$42.91	$42.90	$42.90
Purchase #6	$153.42	11.341%	$170.8194	$170.82	$170.80	$170.80
Purchase #7	$98.70	6.304%	$104.922	$104.92	$104.90	$104.90
7 purchase totals =	$867.72		$938.2078	$938.21	$938.15	$938.20