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	$152.70	10.287%	$168.4082	$168.41	$168.40	$168.40
Purchase #2	$214.65	3.678%	$222.5448	$222.54	$222.55	$222.50
Purchase #3	$204.65	9.576%	$224.2473	$224.25	$224.25	$224.20
Purchase #4	$215.84	9.855%	$237.111	$237.11	$237.10	$237.10
Purchase #5	$45.93	10.692%	$50.8408	$50.84	$50.85	$50.80
Purchase #6	$159.70	7.266%	$171.3038	$171.30	$171.30	$171.30
Purchase #7	$120.33	9.233%	$131.4401	$131.44	$131.45	$131.40
7 purchase totals =	$1,113.80		$1,205.8960	$1,205.89	$1,205.90	$1,205.70