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	$247.45	6.289%	$263.0121	$263.01	$263.00	$263.00
Purchase #2	$231.72	4.480%	$242.1011	$242.10	$242.10	$242.10
Purchase #3	$82.57	9.387%	$90.3208	$90.32	$90.30	$90.30
Purchase #4	$76.85	13.362%	$87.1187	$87.12	$87.10	$87.10
Purchase #5	$19.37	11.287%	$21.5563	$21.56	$21.55	$21.60
Purchase #6	$232.73	12.592%	$262.0354	$262.04	$262.05	$262.00
Purchase #7	$79.29	10.112%	$87.3078	$87.31	$87.30	$87.30
7 purchase totals =	$969.98		$1,053.4522	$1,053.46	$1,053.40	$1,053.40