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	$130.30	8.420%	$141.2713	$141.27	$141.25	$141.30
Purchase #2	$36.30	3.500%	$37.5705	$37.57	$37.55	$37.60
Purchase #3	$180.25	4.573%	$188.4928	$188.49	$188.50	$188.50
Purchase #4	$47.37	12.424%	$53.2552	$53.26	$53.25	$53.30
Purchase #5	$13.31	13.360%	$15.0882	$15.09	$15.10	$15.10
Purchase #6	$205.48	11.474%	$229.0568	$229.06	$229.05	$229.10
Purchase #7	$225.70	5.508%	$238.1316	$238.13	$238.15	$238.10
7 purchase totals =	$838.71		$902.8664	$902.87	$902.85	$903.00