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	$237.33	11.425%	$264.445	$264.45	$264.45	$264.40
Purchase #2	$110.28	6.697%	$117.6655	$117.67	$117.65	$117.70
Purchase #3	$220.64	5.748%	$233.3224	$233.32	$233.30	$233.30
Purchase #4	$75.78	9.608%	$83.0609	$83.06	$83.05	$83.10
Purchase #5	$245.50	4.128%	$255.6342	$255.63	$255.65	$255.60
Purchase #6	$18.85	5.271%	$19.8436	$19.84	$19.85	$19.80
Purchase #7	$97.95	11.724%	$109.4337	$109.43	$109.45	$109.40
7 purchase totals =	$1,006.33		$1,083.4053	$1,083.40	$1,083.40	$1,083.30