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	$178.74	9.787%	$196.2333	$196.23	$196.25	$196.20
Purchase #2	$221.63	9.869%	$243.5027	$243.50	$243.50	$243.50
Purchase #3	$50.77	5.761%	$53.6949	$53.69	$53.70	$53.70
Purchase #4	$45.98	12.659%	$51.8006	$51.80	$51.80	$51.80
Purchase #5	$70.59	13.470%	$80.0985	$80.10	$80.10	$80.10
Purchase #6	$98.74	7.263%	$105.9115	$105.91	$105.90	$105.90
Purchase #7	$76.30	9.282%	$83.3822	$83.38	$83.40	$83.40
7 purchase totals =	$742.75		$814.6237	$814.61	$814.65	$814.60