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	$59.69	7.756%	$64.3196	$64.32	$64.30	$64.30
Purchase #2	$186.63	5.188%	$196.3124	$196.31	$196.30	$196.30
Purchase #3	$147.85	5.614%	$156.1503	$156.15	$156.15	$156.20
Purchase #4	$175.52	4.539%	$183.4869	$183.49	$183.50	$183.50
Purchase #5	$100.41	10.273%	$110.7251	$110.73	$110.75	$110.70
Purchase #6	$179.88	5.625%	$189.9983	$190.00	$190.00	$190.00
Purchase #7	$142.29	10.758%	$157.5976	$157.60	$157.60	$157.60
7 purchase totals =	$992.27		$1,058.5902	$1,058.60	$1,058.60	$1,058.60