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	$114.65	11.600%	$127.9494	$127.95	$127.95	$127.90
Purchase #2	$150.30	13.782%	$171.0143	$171.01	$171.00	$171.00
Purchase #3	$88.94	11.862%	$99.4901	$99.49	$99.50	$99.50
Purchase #4	$69.61	11.784%	$77.8128	$77.81	$77.80	$77.80
Purchase #5	$154.71	5.237%	$162.8122	$162.81	$162.80	$162.80
Purchase #6	$122.46	11.525%	$136.5735	$136.57	$136.55	$136.60
Purchase #7	$60.38	7.814%	$65.0981	$65.10	$65.10	$65.10
7 purchase totals =	$761.05		$840.7504	$840.74	$840.70	$840.70