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	$110.51	5.651%	$116.7549	$116.75	$116.75	$116.80
Purchase #2	$92.50	8.747%	$100.591	$100.59	$100.60	$100.60
Purchase #3	$219.85	4.807%	$230.4182	$230.42	$230.40	$230.40
Purchase #4	$94.46	6.608%	$100.7019	$100.70	$100.70	$100.70
Purchase #5	$214.65	4.180%	$223.6224	$223.62	$223.60	$223.60
Purchase #6	$239.51	9.852%	$263.1065	$263.11	$263.10	$263.10
Purchase #7	$55.69	9.686%	$61.0841	$61.08	$61.10	$61.10
7 purchase totals =	$1,027.17		$1,096.2790	$1,096.27	$1,096.25	$1,096.30