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	$209.31	12.415%	$235.2958	$235.30	$235.30	$235.30
Purchase #2	$111.33	11.641%	$124.2899	$124.29	$124.30	$124.30
Purchase #3	$201.67	10.112%	$222.0629	$222.06	$222.05	$222.10
Purchase #4	$75.25	11.120%	$83.6178	$83.62	$83.60	$83.60
Purchase #5	$75.54	3.755%	$78.3765	$78.38	$78.40	$78.40
Purchase #6	$216.26	12.106%	$242.4404	$242.44	$242.45	$242.40
Purchase #7	$222.47	3.329%	$229.876	$229.88	$229.90	$229.90
7 purchase totals =	$1,111.83		$1,215.9593	$1,215.97	$1,216.00	$1,216.00