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	$101.41	10.571%	$112.1301	$112.13	$112.15	$112.10
Purchase #2	$78.88	9.645%	$86.488	$86.49	$86.50	$86.50
Purchase #3	$73.68	13.253%	$83.4448	$83.44	$83.45	$83.40
Purchase #4	$212.31	7.177%	$227.5475	$227.55	$227.55	$227.50
Purchase #5	$42.95	10.393%	$47.4138	$47.41	$47.40	$47.40
Purchase #6	$86.34	10.353%	$95.2788	$95.28	$95.30	$95.30
Purchase #7	$109.62	10.278%	$120.8867	$120.89	$120.90	$120.90
7 purchase totals =	$705.19		$773.1897	$773.19	$773.25	$773.10