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	$179.56	5.146%	$188.8002	$188.80	$188.80	$188.80
Purchase #2	$52.46	11.230%	$58.3513	$58.35	$58.35	$58.40
Purchase #3	$70.56	10.543%	$77.9991	$78.00	$78.00	$78.00
Purchase #4	$198.51	6.218%	$210.8534	$210.85	$210.85	$210.90
Purchase #5	$39.64	8.721%	$43.097	$43.10	$43.10	$43.10
Purchase #6	$217.76	7.425%	$233.9287	$233.93	$233.95	$233.90
Purchase #7	$210.54	7.156%	$225.6062	$225.61	$225.60	$225.60
7 purchase totals =	$969.03		$1,038.6359	$1,038.64	$1,038.65	$1,038.70