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	$64.85	7.208%	$69.5244	$69.52	$69.50	$69.50
Purchase #2	$224.43	11.538%	$250.3247	$250.32	$250.30	$250.30
Purchase #3	$114.98	7.627%	$123.7495	$123.75	$123.75	$123.70
Purchase #4	$177.38	6.735%	$189.3265	$189.33	$189.35	$189.30
Purchase #5	$144.41	4.593%	$151.0428	$151.04	$151.05	$151.00
Purchase #6	$22.72	8.352%	$24.6176	$24.62	$24.60	$24.60
Purchase #7	$250.91	5.454%	$264.5946	$264.59	$264.60	$264.60
7 purchase totals =	$999.68		$1,073.1801	$1,073.17	$1,073.15	$1,073.00