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	$84.56	9.237%	$92.3708	$92.37	$92.35	$92.40
Purchase #2	$49.41	5.550%	$52.1523	$52.15	$52.15	$52.20
Purchase #3	$52.91	3.709%	$54.8724	$54.87	$54.85	$54.90
Purchase #4	$172.88	4.802%	$181.1817	$181.18	$181.20	$181.20
Purchase #5	$67.77	6.300%	$72.0395	$72.04	$72.05	$72.00
Purchase #6	$92.76	3.757%	$96.245	$96.25	$96.25	$96.20
Purchase #7	$71.62	10.472%	$79.12	$79.12	$79.10	$79.10
7 purchase totals =	$591.91		$627.9817	$627.98	$627.95	$628.00