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	$125.40	7.395%	$134.6733	$134.67	$134.65	$134.70
Purchase #2	$105.37	4.263%	$109.8619	$109.86	$109.85	$109.90
Purchase #3	$223.67	5.720%	$236.4639	$236.46	$236.45	$236.50
Purchase #4	$95.28	9.231%	$104.0753	$104.08	$104.10	$104.10
Purchase #5	$89.88	11.692%	$100.3888	$100.39	$100.40	$100.40
Purchase #6	$207.77	11.561%	$231.7903	$231.79	$231.80	$231.80
Purchase #7	$234.80	4.578%	$245.5491	$245.55	$245.55	$245.50
7 purchase totals =	$1,082.17		$1,162.8026	$1,162.80	$1,162.80	$1,162.90