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	$177.90	5.677%	$187.9994	$188.00	$188.00	$188.00
Purchase #2	$162.73	13.399%	$184.5342	$184.53	$184.55	$184.50
Purchase #3	$149.47	10.403%	$165.0194	$165.02	$165.00	$165.00
Purchase #4	$206.60	10.653%	$228.6091	$228.61	$228.60	$228.60
Purchase #5	$180.89	10.741%	$200.3194	$200.32	$200.30	$200.30
Purchase #6	$184.69	8.574%	$200.5253	$200.53	$200.55	$200.50
Purchase #7	$46.97	11.553%	$52.3964	$52.40	$52.40	$52.40
7 purchase totals =	$1,109.25		$1,219.4032	$1,219.41	$1,219.40	$1,219.30