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	$215.76	6.567%	$229.929	$229.93	$229.95	$229.90
Purchase #2	$219.85	13.601%	$249.7518	$249.75	$249.75	$249.80
Purchase #3	$170.84	8.365%	$185.1308	$185.13	$185.15	$185.10
Purchase #4	$74.41	10.839%	$82.4753	$82.48	$82.50	$82.50
Purchase #5	$89.44	9.424%	$97.8688	$97.87	$97.85	$97.90
Purchase #6	$172.89	13.381%	$196.0244	$196.02	$196.00	$196.00
Purchase #7	$35.75	5.668%	$37.7763	$37.78	$37.80	$37.80
7 purchase totals =	$978.94		$1,078.9564	$1,078.96	$1,079.00	$1,079.00