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	$226.73	9.243%	$247.6867	$247.69	$247.70	$247.70
Purchase #2	$83.55	13.158%	$94.5435	$94.54	$94.55	$94.50
Purchase #3	$112.25	13.856%	$127.8034	$127.80	$127.80	$127.80
Purchase #4	$71.38	11.329%	$79.4666	$79.47	$79.45	$79.50
Purchase #5	$212.29	12.455%	$238.7307	$238.73	$238.75	$238.70
Purchase #6	$89.32	11.816%	$99.8741	$99.87	$99.85	$99.90
Purchase #7	$236.82	13.167%	$268.0021	$268.00	$268.00	$268.00
7 purchase totals =	$1,032.34		$1,156.1071	$1,156.10	$1,156.10	$1,156.10