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	$170.52	11.360%	$189.8911	$189.89	$189.90	$189.90
Purchase #2	$13.61	5.387%	$14.3432	$14.34	$14.35	$14.30
Purchase #3	$7.37	12.431%	$8.2862	$8.29	$8.30	$8.30
Purchase #4	$54.45	11.618%	$60.776	$60.78	$60.80	$60.80
Purchase #5	$56.99	12.558%	$64.1468	$64.15	$64.15	$64.10
Purchase #6	$29.38	10.499%	$32.4646	$32.46	$32.45	$32.50
Purchase #7	$13.59	5.109%	$14.2843	$14.28	$14.30	$14.30
7 purchase totals =	$345.91		$384.1922	$384.19	$384.25	$384.20