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	$180.49	7.299%	$193.664	$193.66	$193.65	$193.70
Purchase #2	$76.56	6.166%	$81.2807	$81.28	$81.30	$81.30
Purchase #3	$172.67	10.300%	$190.455	$190.46	$190.45	$190.50
Purchase #4	$91.25	5.794%	$96.537	$96.54	$96.55	$96.50
Purchase #5	$90.43	10.407%	$99.8411	$99.84	$99.85	$99.80
Purchase #6	$68.71	5.809%	$72.7014	$72.70	$72.70	$72.70
Purchase #7	$73.48	7.450%	$78.9543	$78.95	$78.95	$79.00
7 purchase totals =	$753.59		$813.4335	$813.43	$813.45	$813.50