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	$100.38	5.377%	$105.7774	$105.78	$105.80	$105.80
Purchase #2	$112.92	3.519%	$116.8937	$116.89	$116.90	$116.90
Purchase #3	$192.63	8.256%	$208.5335	$208.53	$208.55	$208.50
Purchase #4	$169.31	12.825%	$191.024	$191.02	$191.00	$191.00
Purchase #5	$91.97	4.502%	$96.1105	$96.11	$96.10	$96.10
Purchase #6	$182.64	5.647%	$192.9537	$192.95	$192.95	$193.00
Purchase #7	$181.57	4.358%	$189.4828	$189.48	$189.50	$189.50
7 purchase totals =	$1,031.42		$1,100.7756	$1,100.76	$1,100.80	$1,100.80