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	$54.46	9.762%	$59.7764	$59.78	$59.80	$59.80
Purchase #2	$241.27	5.219%	$253.8619	$253.86	$253.85	$253.90
Purchase #3	$82.78	4.193%	$86.251	$86.25	$86.25	$86.30
Purchase #4	$122.76	4.371%	$128.1258	$128.13	$128.15	$128.10
Purchase #5	$16.62	13.151%	$18.8057	$18.81	$18.80	$18.80
Purchase #6	$122.78	11.370%	$136.7401	$136.74	$136.75	$136.70
Purchase #7	$72.49	9.365%	$79.2787	$79.28	$79.30	$79.30
7 purchase totals =	$713.16		$762.8396	$762.85	$762.90	$762.90