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	$126.68	11.430%	$141.1595	$141.16	$141.15	$141.20
Purchase #2	$47.64	13.588%	$54.1133	$54.11	$54.10	$54.10
Purchase #3	$151.77	4.455%	$158.5314	$158.53	$158.55	$158.50
Purchase #4	$209.28	6.758%	$223.4231	$223.42	$223.40	$223.40
Purchase #5	$250.82	5.599%	$264.8634	$264.86	$264.85	$264.90
Purchase #6	$76.61	6.777%	$81.8019	$81.80	$81.80	$81.80
Purchase #7	$115.79	9.440%	$126.7206	$126.72	$126.70	$126.70
7 purchase totals =	$978.59		$1,050.6132	$1,050.60	$1,050.55	$1,050.60