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	$186.86	12.495%	$210.2082	$210.21	$210.20	$210.20
Purchase #2	$83.72	8.705%	$91.0078	$91.01	$91.00	$91.00
Purchase #3	$212.85	10.661%	$235.5419	$235.54	$235.55	$235.50
Purchase #4	$93.36	13.380%	$105.8516	$105.85	$105.85	$105.90
Purchase #5	$24.89	10.130%	$27.4114	$27.41	$27.40	$27.40
Purchase #6	$229.60	11.387%	$255.7446	$255.74	$255.75	$255.70
Purchase #7	$104.61	4.306%	$109.1145	$109.11	$109.10	$109.10
7 purchase totals =	$935.89		$1,034.8800	$1,034.87	$1,034.85	$1,034.80