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	$109.70	12.240%	$123.1273	$123.13	$123.15	$123.10
Purchase #2	$107.74	4.486%	$112.5732	$112.57	$112.55	$112.60
Purchase #3	$164.69	5.812%	$174.2618	$174.26	$174.25	$174.30
Purchase #4	$237.88	13.828%	$270.774	$270.77	$270.75	$270.80
Purchase #5	$185.79	7.429%	$199.5923	$199.59	$199.60	$199.60
Purchase #6	$224.83	4.217%	$234.3111	$234.31	$234.30	$234.30
Purchase #7	$98.33	13.471%	$111.576	$111.58	$111.60	$111.60
7 purchase totals =	$1,128.96		$1,226.2157	$1,226.21	$1,226.20	$1,226.30