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	$194.79	5.798%	$206.0839	$206.08	$206.10	$206.10
Purchase #2	$20.27	3.221%	$20.9229	$20.92	$20.90	$20.90
Purchase #3	$128.61	3.358%	$132.9287	$132.93	$132.95	$132.90
Purchase #4	$85.93	4.472%	$89.7728	$89.77	$89.75	$89.80
Purchase #5	$58.34	10.695%	$64.5795	$64.58	$64.60	$64.60
Purchase #6	$54.33	10.181%	$59.8613	$59.86	$59.85	$59.90
Purchase #7	$58.44	10.710%	$64.6989	$64.70	$64.70	$64.70
7 purchase totals =	$600.71		$638.8480	$638.84	$638.85	$638.90