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	$71.54	7.363%	$76.8075	$76.81	$76.80	$76.80
Purchase #2	$96.41	13.618%	$109.5391	$109.54	$109.55	$109.50
Purchase #3	$148.88	6.273%	$158.2192	$158.22	$158.20	$158.20
Purchase #4	$134.82	11.550%	$150.3917	$150.39	$150.40	$150.40
Purchase #5	$234.80	5.395%	$247.4675	$247.47	$247.45	$247.50
Purchase #6	$54.45	7.199%	$58.3699	$58.37	$58.35	$58.40
Purchase #7	$233.68	11.662%	$260.9318	$260.93	$260.95	$260.90
7 purchase totals =	$974.58		$1,061.7267	$1,061.73	$1,061.70	$1,061.70