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	$119.31	7.650%	$128.4372	$128.44	$128.45	$128.40
Purchase #2	$94.42	9.123%	$103.0339	$103.03	$103.05	$103.00
Purchase #3	$117.43	6.352%	$124.8892	$124.89	$124.90	$124.90
Purchase #4	$126.92	12.224%	$142.4347	$142.43	$142.45	$142.40
Purchase #5	$166.27	3.359%	$171.855	$171.86	$171.85	$171.90
Purchase #6	$108.74	5.606%	$114.836	$114.84	$114.85	$114.80
Purchase #7	$190.28	11.106%	$211.4125	$211.41	$211.40	$211.40
7 purchase totals =	$923.37		$996.8985	$996.90	$996.95	$996.80