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	$90.44	13.653%	$102.7878	$102.79	$102.80	$102.80
Purchase #2	$241.60	5.632%	$255.2069	$255.21	$255.20	$255.20
Purchase #3	$241.73	4.685%	$253.0551	$253.06	$253.05	$253.10
Purchase #4	$210.79	6.686%	$224.8834	$224.88	$224.90	$224.90
Purchase #5	$150.97	13.450%	$171.2755	$171.28	$171.30	$171.30
Purchase #6	$64.94	11.668%	$72.5172	$72.52	$72.50	$72.50
Purchase #7	$83.39	13.401%	$94.5651	$94.57	$94.55	$94.60
7 purchase totals =	$1,083.86		$1,174.2910	$1,174.31	$1,174.30	$1,174.40