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	$95.33	4.195%	$99.3291	$99.33	$99.35	$99.30
Purchase #2	$215.56	8.216%	$233.2704	$233.27	$233.25	$233.30
Purchase #3	$121.32	7.494%	$130.4117	$130.41	$130.40	$130.40
Purchase #4	$60.27	13.279%	$68.2733	$68.27	$68.25	$68.30
Purchase #5	$215.68	10.302%	$237.8994	$237.90	$237.90	$237.90
Purchase #6	$71.85	6.615%	$76.6029	$76.60	$76.60	$76.60
Purchase #7	$198.48	4.674%	$207.757	$207.76	$207.75	$207.80
7 purchase totals =	$978.49		$1,053.5438	$1,053.54	$1,053.50	$1,053.60