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	$69.68	10.676%	$77.119	$77.12	$77.10	$77.10
Purchase #2	$246.42	3.651%	$255.4168	$255.42	$255.40	$255.40
Purchase #3	$85.83	4.496%	$89.6889	$89.69	$89.70	$89.70
Purchase #4	$234.95	9.736%	$257.8247	$257.82	$257.80	$257.80
Purchase #5	$241.57	4.409%	$252.2208	$252.22	$252.20	$252.20
Purchase #6	$89.83	9.752%	$98.5902	$98.59	$98.60	$98.60
Purchase #7	$73.41	11.276%	$81.6877	$81.69	$81.70	$81.70
7 purchase totals =	$1,041.69		$1,112.5481	$1,112.55	$1,112.50	$1,112.50