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	$42.36	3.230%	$43.7282	$43.73	$43.75	$43.70
Purchase #2	$113.65	4.520%	$118.787	$118.79	$118.80	$118.80
Purchase #3	$145.46	7.108%	$155.7993	$155.80	$155.80	$155.80
Purchase #4	$232.98	6.655%	$248.4848	$248.48	$248.50	$248.50
Purchase #5	$176.98	4.628%	$185.1706	$185.17	$185.15	$185.20
Purchase #6	$173.54	3.414%	$179.4647	$179.46	$179.45	$179.50
Purchase #7	$143.38	13.482%	$162.7105	$162.71	$162.70	$162.70
7 purchase totals =	$1,028.35		$1,094.1451	$1,094.14	$1,094.15	$1,094.20