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	$59.54	12.121%	$66.7568	$66.76	$66.75	$66.80
Purchase #2	$184.58	7.548%	$198.5121	$198.51	$198.50	$198.50
Purchase #3	$210.74	12.598%	$237.289	$237.29	$237.30	$237.30
Purchase #4	$64.65	8.290%	$70.0095	$70.01	$70.00	$70.00
Purchase #5	$181.97	4.403%	$189.9821	$189.98	$190.00	$190.00
Purchase #6	$91.47	7.327%	$98.172	$98.17	$98.15	$98.20
Purchase #7	$223.76	4.392%	$233.5875	$233.59	$233.60	$233.60
7 purchase totals =	$1,016.71		$1,094.3090	$1,094.31	$1,094.30	$1,094.40