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	$58.76	4.493%	$61.4001	$61.40	$61.40	$61.40
Purchase #2	$18.59	3.742%	$19.2856	$19.29	$19.30	$19.30
Purchase #3	$65.64	5.461%	$69.2246	$69.22	$69.20	$69.20
Purchase #4	$85.96	4.674%	$89.9778	$89.98	$90.00	$90.00
Purchase #5	$227.98	7.475%	$245.0215	$245.02	$245.00	$245.00
Purchase #6	$64.55	11.791%	$72.1611	$72.16	$72.15	$72.20
Purchase #7	$45.94	11.809%	$51.3651	$51.37	$51.35	$51.40
7 purchase totals =	$567.42		$608.4358	$608.44	$608.40	$608.50