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	$53.55	11.243%	$59.5706	$59.57	$59.55	$59.60
Purchase #2	$123.94	6.304%	$131.7532	$131.75	$131.75	$131.80
Purchase #3	$204.35	5.501%	$215.5913	$215.59	$215.60	$215.60
Purchase #4	$64.72	10.782%	$71.6981	$71.70	$71.70	$71.70
Purchase #5	$96.41	3.324%	$99.6147	$99.61	$99.60	$99.60
Purchase #6	$82.74	12.548%	$93.1222	$93.12	$93.10	$93.10
Purchase #7	$167.67	3.851%	$174.127	$174.13	$174.15	$174.10
7 purchase totals =	$793.38		$845.4771	$845.47	$845.45	$845.50