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	$181.61	6.608%	$193.6108	$193.61	$193.60	$193.60
Purchase #2	$74.39	12.507%	$83.694	$83.69	$83.70	$83.70
Purchase #3	$100.82	10.481%	$111.3869	$111.39	$111.40	$111.40
Purchase #4	$179.80	4.765%	$188.3675	$188.37	$188.35	$188.40
Purchase #5	$95.89	11.175%	$106.6057	$106.61	$106.60	$106.60
Purchase #6	$81.97	6.519%	$87.3136	$87.31	$87.30	$87.30
Purchase #7	$148.63	4.661%	$155.5576	$155.56	$155.55	$155.60
7 purchase totals =	$863.11		$926.5361	$926.54	$926.50	$926.60