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	$105.47	7.400%	$113.2748	$113.27	$113.25	$113.30
Purchase #2	$96.63	10.352%	$106.6331	$106.63	$106.65	$106.60
Purchase #3	$99.50	7.185%	$106.6491	$106.65	$106.65	$106.60
Purchase #4	$76.90	7.183%	$82.4237	$82.42	$82.40	$82.40
Purchase #5	$27.91	8.487%	$30.2787	$30.28	$30.30	$30.30
Purchase #6	$107.80	3.466%	$111.5363	$111.54	$111.55	$111.50
Purchase #7	$11.31	4.623%	$11.8329	$11.83	$11.85	$11.80
7 purchase totals =	$525.52		$562.6286	$562.62	$562.65	$562.50