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	$61.98	8.789%	$67.4274	$67.43	$67.45	$67.40
Purchase #2	$218.82	13.153%	$247.6014	$247.60	$247.60	$247.60
Purchase #3	$189.36	13.573%	$215.0618	$215.06	$215.05	$215.10
Purchase #4	$233.52	7.384%	$250.7631	$250.76	$250.75	$250.80
Purchase #5	$57.98	3.205%	$59.8383	$59.84	$59.85	$59.80
Purchase #6	$209.98	5.164%	$220.8234	$220.82	$220.80	$220.80
Purchase #7	$219.68	13.355%	$249.0183	$249.02	$249.00	$249.00
7 purchase totals =	$1,191.32		$1,310.5337	$1,310.53	$1,310.50	$1,310.50