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	$55.54	7.624%	$59.7744	$59.77	$59.75	$59.80
Purchase #2	$68.49	7.229%	$73.4411	$73.44	$73.45	$73.40
Purchase #3	$123.35	3.214%	$127.3145	$127.31	$127.30	$127.30
Purchase #4	$203.82	11.792%	$227.8545	$227.85	$227.85	$227.90
Purchase #5	$162.89	11.347%	$181.3731	$181.37	$181.35	$181.40
Purchase #6	$97.31	3.556%	$100.7703	$100.77	$100.75	$100.80
Purchase #7	$47.90	6.253%	$50.8952	$50.90	$50.90	$50.90
7 purchase totals =	$759.30		$821.4231	$821.41	$821.35	$821.50