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	$67.84	4.248%	$70.7218	$70.72	$70.70	$70.70
Purchase #2	$82.90	8.394%	$89.8586	$89.86	$89.85	$89.90
Purchase #3	$127.92	11.645%	$142.8163	$142.82	$142.80	$142.80
Purchase #4	$88.84	5.540%	$93.7617	$93.76	$93.75	$93.80
Purchase #5	$167.41	3.373%	$173.0567	$173.06	$173.05	$173.10
Purchase #6	$112.43	11.175%	$124.9941	$124.99	$125.00	$125.00
Purchase #7	$57.76	6.576%	$61.5583	$61.56	$61.55	$61.60
7 purchase totals =	$705.10		$756.7675	$756.77	$756.70	$756.90