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	$149.65	4.592%	$156.5219	$156.52	$156.50	$156.50
Purchase #2	$77.34	7.363%	$83.0345	$83.03	$83.05	$83.00
Purchase #3	$116.28	5.841%	$123.0719	$123.07	$123.05	$123.10
Purchase #4	$211.47	7.751%	$227.861	$227.86	$227.85	$227.90
Purchase #5	$178.76	9.358%	$195.4884	$195.49	$195.50	$195.50
Purchase #6	$216.55	3.414%	$223.943	$223.94	$223.95	$223.90
Purchase #7	$117.26	12.873%	$132.3549	$132.35	$132.35	$132.40
7 purchase totals =	$1,067.31		$1,142.2756	$1,142.26	$1,142.25	$1,142.30