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	$82.84	9.553%	$90.7537	$90.75	$90.75	$90.80
Purchase #2	$239.26	10.198%	$263.6597	$263.66	$263.65	$263.70
Purchase #3	$101.55	3.578%	$105.1835	$105.18	$105.20	$105.20
Purchase #4	$69.27	13.361%	$78.5252	$78.53	$78.55	$78.50
Purchase #5	$223.48	7.721%	$240.7349	$240.73	$240.75	$240.70
Purchase #6	$118.56	8.672%	$128.8415	$128.84	$128.85	$128.80
Purchase #7	$219.43	10.725%	$242.9639	$242.96	$242.95	$243.00
7 purchase totals =	$1,054.39		$1,150.6624	$1,150.65	$1,150.70	$1,150.70