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	$84.88	12.104%	$95.1539	$95.15	$95.15	$95.20
Purchase #2	$198.83	4.183%	$207.1471	$207.15	$207.15	$207.10
Purchase #3	$94.28	5.445%	$99.4135	$99.41	$99.40	$99.40
Purchase #4	$141.59	7.467%	$152.1625	$152.16	$152.15	$152.20
Purchase #5	$122.82	4.723%	$128.6208	$128.62	$128.60	$128.60
Purchase #6	$50.26	4.793%	$52.669	$52.67	$52.65	$52.70
Purchase #7	$48.83	11.746%	$54.5656	$54.57	$54.55	$54.60
7 purchase totals =	$741.49		$789.7324	$789.73	$789.65	$789.80