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	$88.66	9.346%	$96.9462	$96.95	$96.95	$96.90
Purchase #2	$90.76	12.816%	$102.3918	$102.39	$102.40	$102.40
Purchase #3	$202.26	12.379%	$227.2978	$227.30	$227.30	$227.30
Purchase #4	$37.57	12.552%	$42.2858	$42.29	$42.30	$42.30
Purchase #5	$25.61	3.536%	$26.5156	$26.52	$26.50	$26.50
Purchase #6	$38.63	3.243%	$39.8828	$39.88	$39.90	$39.90
Purchase #7	$53.41	10.841%	$59.2002	$59.20	$59.20	$59.20
7 purchase totals =	$536.90		$594.5202	$594.53	$594.55	$594.50