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	$219.71	6.510%	$234.0131	$234.01	$234.00	$234.00
Purchase #2	$152.39	11.113%	$169.3251	$169.33	$169.35	$169.30
Purchase #3	$118.96	12.518%	$133.8514	$133.85	$133.85	$133.90
Purchase #4	$11.84	3.647%	$12.2718	$12.27	$12.25	$12.30
Purchase #5	$148.65	6.428%	$158.2052	$158.21	$158.20	$158.20
Purchase #6	$213.69	4.285%	$222.8466	$222.85	$222.85	$222.80
Purchase #7	$159.46	8.649%	$173.2517	$173.25	$173.25	$173.30
7 purchase totals =	$1,024.70		$1,103.7649	$1,103.77	$1,103.75	$1,103.80