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	$111.92	11.785%	$125.1098	$125.11	$125.10	$125.10
Purchase #2	$134.67	3.598%	$139.5154	$139.52	$139.50	$139.50
Purchase #3	$159.75	11.784%	$178.5749	$178.57	$178.55	$178.60
Purchase #4	$80.56	6.613%	$85.8874	$85.89	$85.90	$85.90
Purchase #5	$208.40	3.366%	$215.4147	$215.41	$215.40	$215.40
Purchase #6	$95.43	3.248%	$98.5296	$98.53	$98.55	$98.50
Purchase #7	$78.88	4.842%	$82.6994	$82.70	$82.70	$82.70
7 purchase totals =	$869.61		$925.7312	$925.73	$925.70	$925.70