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	$104.44	8.439%	$113.2537	$113.25	$113.25	$113.30
Purchase #2	$233.82	4.212%	$243.6685	$243.67	$243.65	$243.70
Purchase #3	$88.43	12.425%	$99.4174	$99.42	$99.40	$99.40
Purchase #4	$57.69	3.568%	$59.7484	$59.75	$59.75	$59.70
Purchase #5	$216.46	10.547%	$239.29	$239.29	$239.30	$239.30
Purchase #6	$243.89	4.789%	$255.5699	$255.57	$255.55	$255.60
Purchase #7	$74.86	11.717%	$83.6313	$83.63	$83.65	$83.60
7 purchase totals =	$1,019.59		$1,094.5792	$1,094.58	$1,094.55	$1,094.60