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	$95.79	7.107%	$102.5978	$102.60	$102.60	$102.60
Purchase #2	$108.92	11.416%	$121.3543	$121.35	$121.35	$121.40
Purchase #3	$221.35	5.709%	$233.9869	$233.99	$234.00	$234.00
Purchase #4	$78.87	13.803%	$89.7564	$89.76	$89.75	$89.80
Purchase #5	$95.38	10.444%	$105.3415	$105.34	$105.35	$105.30
Purchase #6	$19.54	8.723%	$21.2445	$21.24	$21.25	$21.20
Purchase #7	$144.66	5.461%	$152.5599	$152.56	$152.55	$152.60
7 purchase totals =	$764.51		$826.8413	$826.84	$826.85	$826.90