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	$94.42	5.134%	$99.2675	$99.27	$99.25	$99.30
Purchase #2	$85.92	4.182%	$89.5132	$89.51	$89.50	$89.50
Purchase #3	$34.99	12.638%	$39.412	$39.41	$39.40	$39.40
Purchase #4	$211.28	4.190%	$220.1326	$220.13	$220.15	$220.10
Purchase #5	$53.48	7.564%	$57.5252	$57.53	$57.55	$57.50
Purchase #6	$25.56	10.138%	$28.1513	$28.15	$28.15	$28.20
Purchase #7	$189.47	3.751%	$196.577	$196.58	$196.60	$196.60
7 purchase totals =	$695.12		$730.5788	$730.58	$730.60	$730.60