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	$54.77	3.744%	$56.8206	$56.82	$56.80	$56.80
Purchase #2	$70.55	9.682%	$77.3807	$77.38	$77.40	$77.40
Purchase #3	$143.98	8.676%	$156.4717	$156.47	$156.45	$156.50
Purchase #4	$65.56	6.533%	$69.843	$69.84	$69.85	$69.80
Purchase #5	$198.30	12.532%	$223.151	$223.15	$223.15	$223.20
Purchase #6	$159.93	11.393%	$178.1508	$178.15	$178.15	$178.20
Purchase #7	$59.79	7.818%	$64.4644	$64.46	$64.45	$64.50
7 purchase totals =	$752.88		$826.2822	$826.27	$826.25	$826.40