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	$116.89	11.413%	$130.2307	$130.23	$130.25	$130.20
Purchase #2	$211.31	12.574%	$237.8801	$237.88	$237.90	$237.90
Purchase #3	$238.47	3.336%	$246.4254	$246.43	$246.45	$246.40
Purchase #4	$47.91	12.794%	$54.0396	$54.04	$54.05	$54.00
Purchase #5	$29.69	12.179%	$33.3059	$33.31	$33.30	$33.30
Purchase #6	$24.40	11.140%	$27.1182	$27.12	$27.10	$27.10
Purchase #7	$83.84	4.389%	$87.5197	$87.52	$87.50	$87.50
7 purchase totals =	$752.51		$816.5196	$816.53	$816.55	$816.40