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	$73.50	4.701%	$76.9552	$76.96	$76.95	$77.00
Purchase #2	$125.97	4.343%	$131.4409	$131.44	$131.45	$131.40
Purchase #3	$116.90	12.103%	$131.0484	$131.05	$131.05	$131.00
Purchase #4	$209.51	13.627%	$238.0599	$238.06	$238.05	$238.10
Purchase #5	$52.46	13.259%	$59.4157	$59.42	$59.40	$59.40
Purchase #6	$231.44	4.734%	$242.3964	$242.40	$242.40	$242.40
Purchase #7	$22.91	8.456%	$24.8473	$24.85	$24.85	$24.80
7 purchase totals =	$832.69		$904.1638	$904.18	$904.15	$904.10