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	$69.68	9.119%	$76.0341	$76.03	$76.05	$76.00
Purchase #2	$179.96	8.871%	$195.9243	$195.92	$195.90	$195.90
Purchase #3	$91.90	6.648%	$98.0095	$98.01	$98.00	$98.00
Purchase #4	$37.60	7.104%	$40.2711	$40.27	$40.25	$40.30
Purchase #5	$119.72	9.647%	$131.2694	$131.27	$131.25	$131.30
Purchase #6	$55.73	11.471%	$62.1228	$62.12	$62.10	$62.10
Purchase #7	$145.69	7.677%	$156.8746	$156.87	$156.85	$156.90
7 purchase totals =	$700.28		$760.5058	$760.49	$760.40	$760.50