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	$46.73	11.523%	$52.1147	$52.11	$52.10	$52.10
Purchase #2	$223.54	13.828%	$254.4511	$254.45	$254.45	$254.50
Purchase #3	$236.86	3.796%	$245.8512	$245.85	$245.85	$245.90
Purchase #4	$82.78	11.378%	$92.1987	$92.20	$92.20	$92.20
Purchase #5	$185.55	10.358%	$204.7693	$204.77	$204.75	$204.80
Purchase #6	$228.96	11.541%	$255.3843	$255.38	$255.40	$255.40
Purchase #7	$178.41	11.352%	$198.6631	$198.66	$198.65	$198.70
7 purchase totals =	$1,182.83		$1,303.4324	$1,303.42	$1,303.40	$1,303.60