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	$60.43	6.374%	$64.2818	$64.28	$64.30	$64.30
Purchase #2	$94.46	11.180%	$105.0206	$105.02	$105.00	$105.00
Purchase #3	$142.75	9.745%	$156.661	$156.66	$156.65	$156.70
Purchase #4	$140.34	10.803%	$155.5009	$155.50	$155.50	$155.50
Purchase #5	$189.90	3.602%	$196.7402	$196.74	$196.75	$196.70
Purchase #6	$235.88	10.818%	$261.3975	$261.40	$261.40	$261.40
Purchase #7	$176.27	9.278%	$192.6243	$192.62	$192.60	$192.60
7 purchase totals =	$1,040.03		$1,132.2263	$1,132.22	$1,132.20	$1,132.20