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	$49.65	11.469%	$55.3444	$55.34	$55.35	$55.30
Purchase #2	$33.30	13.698%	$37.8614	$37.86	$37.85	$37.90
Purchase #3	$196.92	12.343%	$221.2258	$221.23	$221.25	$221.20
Purchase #4	$38.58	9.220%	$42.1371	$42.14	$42.15	$42.10
Purchase #5	$150.61	9.223%	$164.5008	$164.50	$164.50	$164.50
Purchase #6	$237.84	13.224%	$269.292	$269.29	$269.30	$269.30
Purchase #7	$50.36	13.803%	$57.3112	$57.31	$57.30	$57.30
7 purchase totals =	$757.26		$847.6727	$847.67	$847.70	$847.60