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	$145.42	13.483%	$165.027	$165.03	$165.05	$165.00
Purchase #2	$142.60	3.727%	$147.9147	$147.91	$147.90	$147.90
Purchase #3	$178.63	10.490%	$197.3683	$197.37	$197.35	$197.40
Purchase #4	$130.42	11.215%	$145.0466	$145.05	$145.05	$145.00
Purchase #5	$219.59	11.123%	$244.015	$244.02	$244.00	$244.00
Purchase #6	$158.42	5.156%	$166.5881	$166.59	$166.60	$166.60
Purchase #7	$52.69	9.684%	$57.7925	$57.79	$57.80	$57.80
7 purchase totals =	$1,027.77		$1,123.7522	$1,123.76	$1,123.75	$1,123.70