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	$135.57	13.277%	$153.5696	$153.57	$153.55	$153.60
Purchase #2	$46.78	8.232%	$50.6309	$50.63	$50.65	$50.60
Purchase #3	$101.85	3.443%	$105.3567	$105.36	$105.35	$105.40
Purchase #4	$127.51	11.539%	$142.2234	$142.22	$142.20	$142.20
Purchase #5	$98.74	4.654%	$103.3354	$103.34	$103.35	$103.30
Purchase #6	$121.31	12.820%	$136.8619	$136.86	$136.85	$136.90
Purchase #7	$37.48	8.615%	$40.7089	$40.71	$40.70	$40.70
7 purchase totals =	$669.24		$732.6868	$732.69	$732.65	$732.70