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	$192.46	9.563%	$210.8649	$210.86	$210.85	$210.90
Purchase #2	$139.70	12.163%	$156.6917	$156.69	$156.70	$156.70
Purchase #3	$168.35	4.714%	$176.286	$176.29	$176.30	$176.30
Purchase #4	$72.98	8.779%	$79.3869	$79.39	$79.40	$79.40
Purchase #5	$136.45	4.446%	$142.5166	$142.52	$142.50	$142.50
Purchase #6	$208.48	8.287%	$225.7567	$225.76	$225.75	$225.80
Purchase #7	$147.45	7.853%	$159.0292	$159.03	$159.05	$159.00
7 purchase totals =	$1,065.87		$1,150.5320	$1,150.54	$1,150.55	$1,150.60