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	$244.43	12.857%	$275.8564	$275.86	$275.85	$275.90
Purchase #2	$223.91	6.524%	$238.5179	$238.52	$238.50	$238.50
Purchase #3	$168.64	13.864%	$192.0202	$192.02	$192.00	$192.00
Purchase #4	$42.78	8.402%	$46.3744	$46.37	$46.35	$46.40
Purchase #5	$117.44	8.385%	$127.2873	$127.29	$127.30	$127.30
Purchase #6	$242.36	6.606%	$258.3703	$258.37	$258.35	$258.40
Purchase #7	$8.47	11.841%	$9.4729	$9.47	$9.45	$9.50
7 purchase totals =	$1,048.03		$1,147.8994	$1,147.90	$1,147.80	$1,148.00