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	$224.86	13.783%	$255.8525	$255.85	$255.85	$255.90
Purchase #2	$200.74	5.223%	$211.2247	$211.22	$211.20	$211.20
Purchase #3	$165.72	3.410%	$171.3711	$171.37	$171.35	$171.40
Purchase #4	$48.48	12.355%	$54.4697	$54.47	$54.45	$54.50
Purchase #5	$85.73	6.824%	$91.5802	$91.58	$91.60	$91.60
Purchase #6	$70.28	8.440%	$76.2116	$76.21	$76.20	$76.20
Purchase #7	$180.97	13.133%	$204.7368	$204.74	$204.75	$204.70
7 purchase totals =	$976.78		$1,065.4466	$1,065.44	$1,065.40	$1,065.50