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	$91.54	7.674%	$98.5648	$98.56	$98.55	$98.60
Purchase #2	$92.61	4.231%	$96.5283	$96.53	$96.55	$96.50
Purchase #3	$160.42	4.351%	$167.3999	$167.40	$167.40	$167.40
Purchase #4	$132.49	6.359%	$140.915	$140.92	$140.90	$140.90
Purchase #5	$124.35	13.793%	$141.5016	$141.50	$141.50	$141.50
Purchase #6	$130.57	7.274%	$140.0677	$140.07	$140.05	$140.10
Purchase #7	$215.74	12.855%	$243.4734	$243.47	$243.45	$243.50
7 purchase totals =	$947.72		$1,028.4507	$1,028.45	$1,028.40	$1,028.50