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	$189.34	3.554%	$196.0691	$196.07	$196.05	$196.10
Purchase #2	$157.44	7.155%	$168.7048	$168.70	$168.70	$168.70
Purchase #3	$83.50	9.525%	$91.4534	$91.45	$91.45	$91.50
Purchase #4	$210.60	5.477%	$222.1346	$222.13	$222.15	$222.10
Purchase #5	$225.73	9.542%	$247.2692	$247.27	$247.25	$247.30
Purchase #6	$62.59	12.244%	$70.2535	$70.25	$70.25	$70.30
Purchase #7	$94.50	3.478%	$97.7867	$97.79	$97.80	$97.80
7 purchase totals =	$1,023.70		$1,093.6713	$1,093.66	$1,093.65	$1,093.80