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	$194.31	11.350%	$216.3642	$216.36	$216.35	$216.40
Purchase #2	$106.77	3.135%	$110.1172	$110.12	$110.10	$110.10
Purchase #3	$173.37	13.519%	$196.8079	$196.81	$196.80	$196.80
Purchase #4	$109.44	13.145%	$123.8259	$123.83	$123.85	$123.80
Purchase #5	$136.51	13.813%	$155.3661	$155.37	$155.35	$155.40
Purchase #6	$113.85	6.376%	$121.1091	$121.11	$121.10	$121.10
Purchase #7	$105.79	6.538%	$112.7066	$112.71	$112.70	$112.70
7 purchase totals =	$940.04		$1,036.2970	$1,036.31	$1,036.25	$1,036.30