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	$181.52	6.299%	$192.9539	$192.95	$192.95	$193.00
Purchase #2	$182.51	4.555%	$190.8233	$190.82	$190.80	$190.80
Purchase #3	$26.76	7.253%	$28.7009	$28.70	$28.70	$28.70
Purchase #4	$6.78	11.609%	$7.5671	$7.57	$7.55	$7.60
Purchase #5	$82.89	13.689%	$94.2368	$94.24	$94.25	$94.20
Purchase #6	$128.25	12.405%	$144.1594	$144.16	$144.15	$144.20
Purchase #7	$126.72	7.698%	$136.4749	$136.47	$136.45	$136.50
7 purchase totals =	$735.43		$794.9163	$794.91	$794.85	$795.00