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	$122.72	4.109%	$127.7626	$127.76	$127.75	$127.80
Purchase #2	$246.47	12.302%	$276.7907	$276.79	$276.80	$276.80
Purchase #3	$167.46	12.538%	$188.4561	$188.46	$188.45	$188.50
Purchase #4	$199.60	12.601%	$224.7516	$224.75	$224.75	$224.80
Purchase #5	$216.66	4.567%	$226.5549	$226.55	$226.55	$226.60
Purchase #6	$106.46	8.530%	$115.541	$115.54	$115.55	$115.50
Purchase #7	$89.54	6.423%	$95.2912	$95.29	$95.30	$95.30
7 purchase totals =	$1,148.91		$1,255.1481	$1,255.14	$1,255.15	$1,255.30