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	$225.69	7.343%	$242.2624	$242.26	$242.25	$242.30
Purchase #2	$54.30	10.140%	$59.806	$59.81	$59.80	$59.80
Purchase #3	$88.44	12.247%	$99.2712	$99.27	$99.25	$99.30
Purchase #4	$122.33	7.764%	$131.8277	$131.83	$131.85	$131.80
Purchase #5	$238.89	12.645%	$269.0976	$269.10	$269.10	$269.10
Purchase #6	$99.87	6.214%	$106.0759	$106.08	$106.10	$106.10
Purchase #7	$204.47	4.161%	$212.978	$212.98	$213.00	$213.00
7 purchase totals =	$1,033.99		$1,121.3188	$1,121.33	$1,121.35	$1,121.40