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	$216.91	7.572%	$233.3344	$233.33	$233.35	$233.30
Purchase #2	$129.76	8.590%	$140.9064	$140.91	$140.90	$140.90
Purchase #3	$91.66	4.618%	$95.8929	$95.89	$95.90	$95.90
Purchase #4	$175.83	8.689%	$191.1079	$191.11	$191.10	$191.10
Purchase #5	$244.63	4.394%	$255.379	$255.38	$255.40	$255.40
Purchase #6	$100.64	11.627%	$112.3414	$112.34	$112.35	$112.30
Purchase #7	$178.86	4.486%	$186.8837	$186.88	$186.90	$186.90
7 purchase totals =	$1,138.29		$1,215.8457	$1,215.84	$1,215.90	$1,215.80