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	$89.91	3.273%	$92.8528	$92.85	$92.85	$92.90
Purchase #2	$44.88	7.574%	$48.2792	$48.28	$48.30	$48.30
Purchase #3	$225.78	5.511%	$238.2227	$238.22	$238.20	$238.20
Purchase #4	$158.83	3.820%	$164.8973	$164.90	$164.90	$164.90
Purchase #5	$218.61	12.217%	$245.3176	$245.32	$245.30	$245.30
Purchase #6	$159.51	5.752%	$168.685	$168.69	$168.70	$168.70
Purchase #7	$58.99	3.128%	$60.8352	$60.84	$60.85	$60.80
7 purchase totals =	$956.51		$1,019.0898	$1,019.10	$1,019.10	$1,019.10