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	$205.75	10.215%	$226.7674	$226.77	$226.75	$226.80
Purchase #2	$216.41	4.382%	$225.8931	$225.89	$225.90	$225.90
Purchase #3	$7.36	5.191%	$7.7421	$7.74	$7.75	$7.70
Purchase #4	$183.40	11.663%	$204.7899	$204.79	$204.80	$204.80
Purchase #5	$194.56	6.339%	$206.8932	$206.89	$206.90	$206.90
Purchase #6	$72.91	13.663%	$82.8717	$82.87	$82.85	$82.90
Purchase #7	$42.72	3.500%	$44.2152	$44.22	$44.20	$44.20
7 purchase totals =	$923.11		$999.1726	$999.17	$999.15	$999.20