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	$179.49	4.391%	$187.3714	$187.37	$187.35	$187.40
Purchase #2	$92.37	7.340%	$99.15	$99.15	$99.15	$99.20
Purchase #3	$185.25	4.701%	$193.9586	$193.96	$193.95	$194.00
Purchase #4	$85.32	8.183%	$92.3017	$92.30	$92.30	$92.30
Purchase #5	$213.50	5.331%	$224.8817	$224.88	$224.90	$224.90
Purchase #6	$95.65	10.461%	$105.6559	$105.66	$105.65	$105.70
Purchase #7	$35.54	4.285%	$37.0629	$37.06	$37.05	$37.10
7 purchase totals =	$887.12		$940.3822	$940.38	$940.35	$940.60