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	$104.80	9.455%	$114.7088	$114.71	$114.70	$114.70
Purchase #2	$212.45	13.113%	$240.3086	$240.31	$240.30	$240.30
Purchase #3	$67.88	7.770%	$73.1543	$73.15	$73.15	$73.20
Purchase #4	$99.35	10.169%	$109.4529	$109.45	$109.45	$109.50
Purchase #5	$191.85	5.373%	$202.1581	$202.16	$202.15	$202.20
Purchase #6	$111.57	6.490%	$118.8109	$118.81	$118.80	$118.80
Purchase #7	$150.69	6.759%	$160.8751	$160.88	$160.90	$160.90
7 purchase totals =	$938.59		$1,019.4687	$1,019.47	$1,019.45	$1,019.60