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	$67.30	3.511%	$69.6629	$69.66	$69.65	$69.70
Purchase #2	$59.50	5.504%	$62.7749	$62.77	$62.75	$62.80
Purchase #3	$225.79	8.648%	$245.3163	$245.32	$245.30	$245.30
Purchase #4	$220.41	13.812%	$250.853	$250.85	$250.85	$250.90
Purchase #5	$139.32	8.580%	$151.2737	$151.27	$151.25	$151.30
Purchase #6	$136.49	11.391%	$152.0376	$152.04	$152.05	$152.00
Purchase #7	$233.72	5.427%	$246.404	$246.40	$246.40	$246.40
7 purchase totals =	$1,082.53		$1,178.3224	$1,178.31	$1,178.25	$1,178.40