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	$220.76	11.116%	$245.2997	$245.30	$245.30	$245.30
Purchase #2	$44.52	5.805%	$47.1044	$47.10	$47.10	$47.10
Purchase #3	$111.96	10.680%	$123.9173	$123.92	$123.90	$123.90
Purchase #4	$160.88	5.609%	$169.9038	$169.90	$169.90	$169.90
Purchase #5	$69.25	3.356%	$71.574	$71.57	$71.55	$71.60
Purchase #6	$171.63	10.321%	$189.3439	$189.34	$189.35	$189.30
Purchase #7	$171.60	4.738%	$179.7304	$179.73	$179.75	$179.70
7 purchase totals =	$950.60		$1,026.8735	$1,026.86	$1,026.85	$1,026.80