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	$88.71	13.801%	$100.9529	$100.95	$100.95	$101.00
Purchase #2	$72.69	3.854%	$75.4915	$75.49	$75.50	$75.50
Purchase #3	$230.56	8.620%	$250.4343	$250.43	$250.45	$250.40
Purchase #4	$54.26	13.524%	$61.5981	$61.60	$61.60	$61.60
Purchase #5	$46.36	13.675%	$52.6997	$52.70	$52.70	$52.70
Purchase #6	$86.57	11.436%	$96.4701	$96.47	$96.45	$96.50
Purchase #7	$94.54	6.114%	$100.3202	$100.32	$100.30	$100.30
7 purchase totals =	$673.69		$737.9668	$737.96	$737.95	$738.00