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	$50.61	7.194%	$54.2509	$54.25	$54.25	$54.30
Purchase #2	$205.78	11.437%	$229.3151	$229.32	$229.30	$229.30
Purchase #3	$158.42	13.162%	$179.2712	$179.27	$179.25	$179.30
Purchase #4	$148.31	10.723%	$164.2133	$164.21	$164.20	$164.20
Purchase #5	$135.29	4.671%	$141.6094	$141.61	$141.60	$141.60
Purchase #6	$45.38	10.611%	$50.1953	$50.20	$50.20	$50.20
Purchase #7	$202.60	4.165%	$211.0383	$211.04	$211.05	$211.00
7 purchase totals =	$946.39		$1,029.8935	$1,029.90	$1,029.85	$1,029.90