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	$238.39	7.342%	$255.8926	$255.89	$255.90	$255.90
Purchase #2	$179.59	8.111%	$194.1565	$194.16	$194.15	$194.20
Purchase #3	$79.71	3.752%	$82.7007	$82.70	$82.70	$82.70
Purchase #4	$144.36	5.577%	$152.411	$152.41	$152.40	$152.40
Purchase #5	$44.36	5.255%	$46.6911	$46.69	$46.70	$46.70
Purchase #6	$249.78	5.406%	$263.2831	$263.28	$263.30	$263.30
Purchase #7	$195.96	9.338%	$214.2587	$214.26	$214.25	$214.30
7 purchase totals =	$1,132.15		$1,209.3937	$1,209.39	$1,209.40	$1,209.50