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	$89.60	11.850%	$100.2176	$100.22	$100.20	$100.20
Purchase #2	$162.49	3.869%	$168.7767	$168.78	$168.80	$168.80
Purchase #3	$191.78	6.599%	$204.4356	$204.44	$204.45	$204.40
Purchase #4	$137.35	9.300%	$150.1236	$150.12	$150.10	$150.10
Purchase #5	$64.67	11.255%	$71.9486	$71.95	$71.95	$71.90
Purchase #6	$88.71	7.341%	$95.2222	$95.22	$95.20	$95.20
Purchase #7	$219.35	6.604%	$233.8359	$233.84	$233.85	$233.80
7 purchase totals =	$953.95		$1,024.5602	$1,024.57	$1,024.55	$1,024.40