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	$184.88	6.218%	$196.3758	$196.38	$196.40	$196.40
Purchase #2	$188.28	5.472%	$198.5827	$198.58	$198.60	$198.60
Purchase #3	$104.37	12.331%	$117.2399	$117.24	$117.25	$117.20
Purchase #4	$65.40	13.325%	$74.1146	$74.11	$74.10	$74.10
Purchase #5	$73.34	12.380%	$82.4195	$82.42	$82.40	$82.40
Purchase #6	$134.67	10.436%	$148.7242	$148.72	$148.70	$148.70
Purchase #7	$55.73	10.516%	$61.5906	$61.59	$61.60	$61.60
7 purchase totals =	$806.67		$879.0473	$879.04	$879.05	$879.00