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	$94.98	10.606%	$105.0536	$105.05	$105.05	$105.10
Purchase #2	$26.95	11.672%	$30.0956	$30.10	$30.10	$30.10
Purchase #3	$164.51	5.556%	$173.6502	$173.65	$173.65	$173.70
Purchase #4	$65.89	9.530%	$72.1693	$72.17	$72.15	$72.20
Purchase #5	$205.55	13.583%	$233.4699	$233.47	$233.45	$233.50
Purchase #6	$59.81	3.330%	$61.8017	$61.80	$61.80	$61.80
Purchase #7	$219.74	13.825%	$250.1191	$250.12	$250.10	$250.10
7 purchase totals =	$837.43		$926.3594	$926.36	$926.30	$926.50