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	$34.56	7.834%	$37.2674	$37.27	$37.25	$37.30
Purchase #2	$94.36	8.374%	$102.2617	$102.26	$102.25	$102.30
Purchase #3	$213.57	4.203%	$222.5463	$222.55	$222.55	$222.50
Purchase #4	$148.30	12.867%	$167.3818	$167.38	$167.40	$167.40
Purchase #5	$16.88	11.130%	$18.7587	$18.76	$18.75	$18.80
Purchase #6	$79.40	13.224%	$89.8999	$89.90	$89.90	$89.90
Purchase #7	$45.84	11.394%	$51.063	$51.06	$51.05	$51.10
7 purchase totals =	$632.91		$689.1788	$689.18	$689.15	$689.30