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	$248.51	6.231%	$263.9947	$263.99	$264.00	$264.00
Purchase #2	$153.86	11.384%	$171.3754	$171.38	$171.40	$171.40
Purchase #3	$34.73	7.262%	$37.2521	$37.25	$37.25	$37.30
Purchase #4	$209.81	5.492%	$221.3328	$221.33	$221.35	$221.30
Purchase #5	$99.69	4.406%	$104.0823	$104.08	$104.10	$104.10
Purchase #6	$135.31	9.433%	$148.0738	$148.07	$148.05	$148.10
Purchase #7	$187.98	5.871%	$199.0163	$199.02	$199.00	$199.00
7 purchase totals =	$1,069.89		$1,145.1274	$1,145.12	$1,145.15	$1,145.20