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	$185.43	3.468%	$191.8607	$191.86	$191.85	$191.90
Purchase #2	$25.30	12.757%	$28.5275	$28.53	$28.55	$28.50
Purchase #3	$31.56	3.265%	$32.5904	$32.59	$32.60	$32.60
Purchase #4	$102.84	12.140%	$115.3248	$115.32	$115.30	$115.30
Purchase #5	$139.31	3.608%	$144.3363	$144.34	$144.35	$144.30
Purchase #6	$226.29	7.548%	$243.3704	$243.37	$243.35	$243.40
Purchase #7	$175.31	10.832%	$194.2996	$194.30	$194.30	$194.30
7 purchase totals =	$886.04		$950.3097	$950.31	$950.30	$950.30