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	$56.83	3.225%	$58.6628	$58.66	$58.65	$58.70
Purchase #2	$218.35	7.495%	$234.7153	$234.72	$234.70	$234.70
Purchase #3	$99.82	4.114%	$103.9266	$103.93	$103.95	$103.90
Purchase #4	$170.38	5.119%	$179.1018	$179.10	$179.10	$179.10
Purchase #5	$180.89	4.378%	$188.8094	$188.81	$188.80	$188.80
Purchase #6	$11.40	7.799%	$12.2891	$12.29	$12.30	$12.30
Purchase #7	$250.32	9.212%	$273.3795	$273.38	$273.40	$273.40
7 purchase totals =	$987.99		$1,050.8845	$1,050.89	$1,050.90	$1,050.90