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	$99.33	6.712%	$105.997	$106.00	$106.00	$106.00
Purchase #2	$142.67	6.255%	$151.594	$151.59	$151.60	$151.60
Purchase #3	$229.74	12.500%	$258.4575	$258.46	$258.45	$258.50
Purchase #4	$184.27	6.254%	$195.7942	$195.79	$195.80	$195.80
Purchase #5	$36.80	9.439%	$40.2736	$40.27	$40.25	$40.30
Purchase #6	$181.69	4.275%	$189.4572	$189.46	$189.45	$189.50
Purchase #7	$182.72	7.522%	$196.4642	$196.46	$196.45	$196.50
7 purchase totals =	$1,057.22		$1,138.0377	$1,138.03	$1,138.00	$1,138.20