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	$9.91	8.316%	$10.7341	$10.73	$10.75	$10.70
Purchase #2	$79.28	11.492%	$88.3909	$88.39	$88.40	$88.40
Purchase #3	$231.56	8.349%	$250.8929	$250.89	$250.90	$250.90
Purchase #4	$123.91	6.218%	$131.6147	$131.61	$131.60	$131.60
Purchase #5	$147.51	10.641%	$163.2065	$163.21	$163.20	$163.20
Purchase #6	$149.32	8.703%	$162.3153	$162.32	$162.30	$162.30
Purchase #7	$245.31	3.501%	$253.8983	$253.90	$253.90	$253.90
7 purchase totals =	$986.80		$1,061.0527	$1,061.05	$1,061.05	$1,061.00