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	$67.47	7.266%	$72.3724	$72.37	$72.35	$72.40
Purchase #2	$219.55	10.845%	$243.3602	$243.36	$243.35	$243.40
Purchase #3	$220.78	11.664%	$246.5318	$246.53	$246.55	$246.50
Purchase #4	$194.55	5.280%	$204.8222	$204.82	$204.80	$204.80
Purchase #5	$242.30	3.755%	$251.3984	$251.40	$251.40	$251.40
Purchase #6	$96.40	4.674%	$100.9057	$100.91	$100.90	$100.90
Purchase #7	$95.90	4.663%	$100.3718	$100.37	$100.35	$100.40
7 purchase totals =	$1,136.95		$1,219.7625	$1,219.76	$1,219.70	$1,219.80