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	$133.93	13.181%	$151.5833	$151.58	$151.60	$151.60
Purchase #2	$147.98	4.823%	$155.1171	$155.12	$155.10	$155.10
Purchase #3	$113.81	3.445%	$117.7308	$117.73	$117.75	$117.70
Purchase #4	$239.33	6.489%	$254.8601	$254.86	$254.85	$254.90
Purchase #5	$230.86	7.779%	$248.8186	$248.82	$248.80	$248.80
Purchase #6	$115.95	6.615%	$123.6201	$123.62	$123.60	$123.60
Purchase #7	$54.39	8.651%	$59.0953	$59.10	$59.10	$59.10
7 purchase totals =	$1,036.25		$1,110.8253	$1,110.83	$1,110.80	$1,110.80