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	$194.72	9.306%	$212.8406	$212.84	$212.85	$212.80
Purchase #2	$208.94	11.602%	$233.1812	$233.18	$233.20	$233.20
Purchase #3	$230.26	8.744%	$250.3939	$250.39	$250.40	$250.40
Purchase #4	$223.77	6.608%	$238.5567	$238.56	$238.55	$238.60
Purchase #5	$73.75	13.211%	$83.4931	$83.49	$83.50	$83.50
Purchase #6	$153.96	5.313%	$162.1399	$162.14	$162.15	$162.10
Purchase #7	$115.37	11.317%	$128.4264	$128.43	$128.45	$128.40
7 purchase totals =	$1,200.77		$1,309.0318	$1,309.03	$1,309.10	$1,309.00