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	$38.42	11.745%	$42.9324	$42.93	$42.95	$42.90
Purchase #2	$145.80	13.324%	$165.2264	$165.23	$165.25	$165.20
Purchase #3	$78.42	3.163%	$80.9004	$80.90	$80.90	$80.90
Purchase #4	$201.79	4.545%	$210.9614	$210.96	$210.95	$211.00
Purchase #5	$91.41	9.540%	$100.1305	$100.13	$100.15	$100.10
Purchase #6	$94.32	13.815%	$107.3503	$107.35	$107.35	$107.40
Purchase #7	$234.47	4.499%	$245.0188	$245.02	$245.00	$245.00
7 purchase totals =	$884.63		$952.5202	$952.52	$952.55	$952.50