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	$182.94	12.595%	$205.9813	$205.98	$206.00	$206.00
Purchase #2	$78.94	13.140%	$89.3127	$89.31	$89.30	$89.30
Purchase #3	$43.83	11.602%	$48.9152	$48.92	$48.90	$48.90
Purchase #4	$234.46	5.481%	$247.3108	$247.31	$247.30	$247.30
Purchase #5	$170.30	9.715%	$186.8446	$186.84	$186.85	$186.80
Purchase #6	$49.89	12.146%	$55.9496	$55.95	$55.95	$55.90
Purchase #7	$99.95	7.300%	$107.2464	$107.25	$107.25	$107.20
7 purchase totals =	$860.31		$941.5606	$941.56	$941.55	$941.40