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	$57.31	3.728%	$59.4465	$59.45	$59.45	$59.40
Purchase #2	$233.63	3.108%	$240.8912	$240.89	$240.90	$240.90
Purchase #3	$69.96	12.605%	$78.7785	$78.78	$78.80	$78.80
Purchase #4	$190.61	8.798%	$207.3799	$207.38	$207.40	$207.40
Purchase #5	$140.73	7.480%	$151.2566	$151.26	$151.25	$151.30
Purchase #6	$200.67	8.275%	$217.2754	$217.28	$217.30	$217.30
Purchase #7	$60.42	8.361%	$65.4717	$65.47	$65.45	$65.50
7 purchase totals =	$953.33		$1,020.4998	$1,020.51	$1,020.55	$1,020.60