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	$115.61	6.445%	$123.0611	$123.06	$123.05	$123.10
Purchase #2	$191.87	10.576%	$212.1622	$212.16	$212.15	$212.20
Purchase #3	$69.70	11.282%	$77.5636	$77.56	$77.55	$77.60
Purchase #4	$152.75	11.391%	$170.1498	$170.15	$170.15	$170.10
Purchase #5	$85.36	4.768%	$89.43	$89.43	$89.45	$89.40
Purchase #6	$163.70	3.194%	$168.9286	$168.93	$168.95	$168.90
Purchase #7	$126.33	10.205%	$139.222	$139.22	$139.20	$139.20
7 purchase totals =	$905.32		$980.5173	$980.51	$980.50	$980.50