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	$141.67	13.473%	$160.7572	$160.76	$160.75	$160.80
Purchase #2	$45.71	13.601%	$51.927	$51.93	$51.95	$51.90
Purchase #3	$194.29	12.387%	$218.3567	$218.36	$218.35	$218.40
Purchase #4	$216.42	12.299%	$243.0375	$243.04	$243.05	$243.00
Purchase #5	$92.91	7.179%	$99.58	$99.58	$99.60	$99.60
Purchase #6	$196.41	13.842%	$223.5971	$223.60	$223.60	$223.60
Purchase #7	$117.26	11.564%	$130.8199	$130.82	$130.80	$130.80
7 purchase totals =	$1,004.67		$1,128.0754	$1,128.09	$1,128.10	$1,128.10