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	$53.72	12.230%	$60.29	$60.29	$60.30	$60.30
Purchase #2	$80.63	10.764%	$89.309	$89.31	$89.30	$89.30
Purchase #3	$50.92	7.564%	$54.7716	$54.77	$54.75	$54.80
Purchase #4	$71.93	9.275%	$78.6015	$78.60	$78.60	$78.60
Purchase #5	$154.75	8.504%	$167.9099	$167.91	$167.90	$167.90
Purchase #6	$198.73	5.667%	$209.992	$209.99	$210.00	$210.00
Purchase #7	$79.32	6.443%	$84.4306	$84.43	$84.45	$84.40
7 purchase totals =	$690.00		$745.3046	$745.30	$745.30	$745.30