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	$55.33	11.151%	$61.4998	$61.50	$61.50	$61.50
Purchase #2	$65.86	10.715%	$72.9169	$72.92	$72.90	$72.90
Purchase #3	$54.32	11.635%	$60.6401	$60.64	$60.65	$60.60
Purchase #4	$146.77	12.627%	$165.3026	$165.30	$165.30	$165.30
Purchase #5	$213.34	7.535%	$229.4152	$229.42	$229.40	$229.40
Purchase #6	$120.63	10.408%	$133.1852	$133.19	$133.20	$133.20
Purchase #7	$142.57	10.421%	$157.4272	$157.43	$157.45	$157.40
7 purchase totals =	$798.82		$880.3870	$880.40	$880.40	$880.30