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	$160.38	8.403%	$173.8567	$173.86	$173.85	$173.90
Purchase #2	$45.65	4.349%	$47.6353	$47.64	$47.65	$47.60
Purchase #3	$242.54	12.750%	$273.4639	$273.46	$273.45	$273.50
Purchase #4	$59.35	10.718%	$65.7111	$65.71	$65.70	$65.70
Purchase #5	$115.33	4.838%	$120.9097	$120.91	$120.90	$120.90
Purchase #6	$141.46	12.717%	$159.4495	$159.45	$159.45	$159.40
Purchase #7	$32.64	3.796%	$33.879	$33.88	$33.90	$33.90
7 purchase totals =	$797.35		$874.9052	$874.91	$874.90	$874.90