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	$158.30	5.357%	$166.7801	$166.78	$166.80	$166.80
Purchase #2	$94.79	4.511%	$99.066	$99.07	$99.05	$99.10
Purchase #3	$113.43	5.543%	$119.7174	$119.72	$119.70	$119.70
Purchase #4	$113.70	8.284%	$123.1189	$123.12	$123.10	$123.10
Purchase #5	$135.72	11.498%	$151.3251	$151.33	$151.35	$151.30
Purchase #6	$166.97	9.313%	$182.5199	$182.52	$182.50	$182.50
Purchase #7	$60.40	8.371%	$65.4561	$65.46	$65.45	$65.50
7 purchase totals =	$843.31		$907.9835	$908.00	$907.95	$908.00