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	$174.55	9.444%	$191.0345	$191.03	$191.05	$191.00
Purchase #2	$38.48	13.621%	$43.7214	$43.72	$43.70	$43.70
Purchase #3	$6.34	12.771%	$7.1497	$7.15	$7.15	$7.10
Purchase #4	$171.40	12.815%	$193.3649	$193.36	$193.35	$193.40
Purchase #5	$97.94	13.709%	$111.3666	$111.37	$111.35	$111.40
Purchase #6	$232.53	12.794%	$262.2799	$262.28	$262.30	$262.30
Purchase #7	$128.89	8.570%	$139.9359	$139.94	$139.95	$139.90
7 purchase totals =	$850.13		$948.8529	$948.85	$948.85	$948.80