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	$116.50	13.236%	$131.9199	$131.92	$131.90	$131.90
Purchase #2	$236.69	7.746%	$255.024	$255.02	$255.00	$255.00
Purchase #3	$80.60	6.479%	$85.8221	$85.82	$85.80	$85.80
Purchase #4	$178.64	8.834%	$194.4211	$194.42	$194.40	$194.40
Purchase #5	$58.45	4.425%	$61.0364	$61.04	$61.05	$61.00
Purchase #6	$10.73	4.287%	$11.19	$11.19	$11.20	$11.20
Purchase #7	$113.70	4.275%	$118.5607	$118.56	$118.55	$118.60
7 purchase totals =	$795.31		$857.9742	$857.97	$857.90	$857.90