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	$94.73	7.190%	$101.5411	$101.54	$101.55	$101.50
Purchase #2	$34.66	6.404%	$36.8796	$36.88	$36.90	$36.90
Purchase #3	$132.98	13.467%	$150.8884	$150.89	$150.90	$150.90
Purchase #4	$210.34	6.189%	$223.3579	$223.36	$223.35	$223.40
Purchase #5	$52.74	13.184%	$59.6932	$59.69	$59.70	$59.70
Purchase #6	$101.52	7.456%	$109.0893	$109.09	$109.10	$109.10
Purchase #7	$149.27	11.842%	$166.9466	$166.95	$166.95	$166.90
7 purchase totals =	$776.24		$848.3961	$848.40	$848.45	$848.40