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	$112.58	4.732%	$117.9073	$117.91	$117.90	$117.90
Purchase #2	$91.86	9.416%	$100.5095	$100.51	$100.50	$100.50
Purchase #3	$99.75	5.136%	$104.8732	$104.87	$104.85	$104.90
Purchase #4	$86.36	10.460%	$95.3933	$95.39	$95.40	$95.40
Purchase #5	$116.79	10.715%	$129.304	$129.30	$129.30	$129.30
Purchase #6	$59.67	10.280%	$65.8041	$65.80	$65.80	$65.80
Purchase #7	$100.65	11.799%	$112.5257	$112.53	$112.55	$112.50
7 purchase totals =	$667.66		$726.3171	$726.31	$726.30	$726.30