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	$193.77	3.256%	$200.0792	$200.08	$200.10	$200.10
Purchase #2	$27.73	7.465%	$29.8	$29.80	$29.80	$29.80
Purchase #3	$69.34	5.224%	$72.9623	$72.96	$72.95	$73.00
Purchase #4	$148.97	11.614%	$166.2714	$166.27	$166.25	$166.30
Purchase #5	$48.28	12.654%	$54.3894	$54.39	$54.40	$54.40
Purchase #6	$95.72	4.606%	$100.1289	$100.13	$100.15	$100.10
Purchase #7	$83.88	8.525%	$91.0308	$91.03	$91.05	$91.00
7 purchase totals =	$667.69		$714.6620	$714.66	$714.70	$714.70