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	$13.74	5.810%	$14.5383	$14.54	$14.55	$14.50
Purchase #2	$147.51	12.466%	$165.8986	$165.90	$165.90	$165.90
Purchase #3	$226.30	7.617%	$243.5373	$243.54	$243.55	$243.50
Purchase #4	$216.81	3.212%	$223.7739	$223.77	$223.75	$223.80
Purchase #5	$106.33	11.828%	$118.9067	$118.91	$118.90	$118.90
Purchase #6	$190.67	13.474%	$216.3609	$216.36	$216.35	$216.40
Purchase #7	$60.63	10.269%	$66.8561	$66.86	$66.85	$66.90
7 purchase totals =	$961.99		$1,049.8718	$1,049.88	$1,049.85	$1,049.90