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	$96.45	13.437%	$109.41	$109.41	$109.40	$109.40
Purchase #2	$31.90	11.490%	$35.5653	$35.57	$35.55	$35.60
Purchase #3	$97.35	12.320%	$109.3435	$109.34	$109.35	$109.30
Purchase #4	$223.58	10.119%	$246.2041	$246.20	$246.20	$246.20
Purchase #5	$100.82	11.552%	$112.4667	$112.47	$112.45	$112.50
Purchase #6	$50.27	5.224%	$52.8961	$52.90	$52.90	$52.90
Purchase #7	$245.69	12.695%	$276.8803	$276.88	$276.90	$276.90
7 purchase totals =	$846.06		$942.7660	$942.77	$942.75	$942.80