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	$238.80	6.755%	$254.9309	$254.93	$254.95	$254.90
Purchase #2	$54.88	8.559%	$59.5772	$59.58	$59.60	$59.60
Purchase #3	$71.86	9.870%	$78.9526	$78.95	$78.95	$79.00
Purchase #4	$241.53	7.563%	$259.7969	$259.80	$259.80	$259.80
Purchase #5	$73.70	12.476%	$82.8948	$82.89	$82.90	$82.90
Purchase #6	$167.88	12.692%	$189.1873	$189.19	$189.20	$189.20
Purchase #7	$169.74	11.593%	$189.418	$189.42	$189.40	$189.40
7 purchase totals =	$1,018.39		$1,114.7577	$1,114.76	$1,114.80	$1,114.80