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	$189.63	12.216%	$212.7952	$212.80	$212.80	$212.80
Purchase #2	$97.44	6.344%	$103.6216	$103.62	$103.60	$103.60
Purchase #3	$186.50	5.420%	$196.6083	$196.61	$196.60	$196.60
Purchase #4	$40.30	13.490%	$45.7365	$45.74	$45.75	$45.70
Purchase #5	$193.59	4.694%	$202.6771	$202.68	$202.70	$202.70
Purchase #6	$165.57	10.234%	$182.5144	$182.51	$182.50	$182.50
Purchase #7	$57.28	7.367%	$61.4998	$61.50	$61.50	$61.50
7 purchase totals =	$930.31		$1,005.4529	$1,005.46	$1,005.45	$1,005.40