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	$139.55	4.139%	$145.326	$145.33	$145.35	$145.30
Purchase #2	$245.35	12.273%	$275.4618	$275.46	$275.45	$275.50
Purchase #3	$166.27	7.325%	$178.4493	$178.45	$178.45	$178.40
Purchase #4	$31.25	13.109%	$35.3466	$35.35	$35.35	$35.30
Purchase #5	$28.88	4.117%	$30.069	$30.07	$30.05	$30.10
Purchase #6	$171.64	5.293%	$180.7249	$180.72	$180.70	$180.70
Purchase #7	$159.99	6.166%	$169.855	$169.86	$169.85	$169.90
7 purchase totals =	$942.93		$1,015.2326	$1,015.24	$1,015.20	$1,015.20