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	$96.41	4.495%	$100.7436	$100.74	$100.75	$100.70
Purchase #2	$51.53	11.529%	$57.4709	$57.47	$57.45	$57.50
Purchase #3	$9.27	10.865%	$10.2772	$10.28	$10.30	$10.30
Purchase #4	$147.50	9.103%	$160.9269	$160.93	$160.95	$160.90
Purchase #5	$216.35	10.630%	$239.348	$239.35	$239.35	$239.30
Purchase #6	$99.50	5.439%	$104.9118	$104.91	$104.90	$104.90
Purchase #7	$79.53	9.323%	$86.9446	$86.94	$86.95	$86.90
7 purchase totals =	$700.09		$760.6230	$760.62	$760.65	$760.50