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	$76.66	8.133%	$82.8948	$82.89	$82.90	$82.90
Purchase #2	$88.91	11.731%	$99.34	$99.34	$99.35	$99.30
Purchase #3	$6.67	10.857%	$7.3942	$7.39	$7.40	$7.40
Purchase #4	$234.32	10.840%	$259.7203	$259.72	$259.70	$259.70
Purchase #5	$245.62	4.187%	$255.9041	$255.90	$255.90	$255.90
Purchase #6	$230.53	7.162%	$247.0406	$247.04	$247.05	$247.00
Purchase #7	$110.31	6.647%	$117.6423	$117.64	$117.65	$117.60
7 purchase totals =	$993.02		$1,069.9363	$1,069.92	$1,069.95	$1,069.80