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	$212.41	8.309%	$230.0591	$230.06	$230.05	$230.10
Purchase #2	$207.77	12.380%	$233.4919	$233.49	$233.50	$233.50
Purchase #3	$69.63	13.112%	$78.7599	$78.76	$78.75	$78.80
Purchase #4	$193.48	3.392%	$200.0428	$200.04	$200.05	$200.00
Purchase #5	$240.38	7.591%	$258.6272	$258.63	$258.65	$258.60
Purchase #6	$158.36	9.115%	$172.7945	$172.79	$172.80	$172.80
Purchase #7	$134.28	13.624%	$152.5743	$152.57	$152.55	$152.60
7 purchase totals =	$1,216.31		$1,326.3497	$1,326.34	$1,326.35	$1,326.40