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	$129.45	10.227%	$142.6889	$142.69	$142.70	$142.70
Purchase #2	$236.95	13.239%	$268.3198	$268.32	$268.30	$268.30
Purchase #3	$183.95	6.717%	$196.3059	$196.31	$196.30	$196.30
Purchase #4	$71.30	7.453%	$76.614	$76.61	$76.60	$76.60
Purchase #5	$68.52	9.446%	$74.9924	$74.99	$75.00	$75.00
Purchase #6	$250.50	5.104%	$263.2855	$263.29	$263.30	$263.30
Purchase #7	$34.93	13.217%	$39.5467	$39.55	$39.55	$39.50
7 purchase totals =	$975.60		$1,061.7532	$1,061.76	$1,061.75	$1,061.70