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	$153.74	9.179%	$167.8518	$167.85	$167.85	$167.90
Purchase #2	$100.59	4.813%	$105.4314	$105.43	$105.45	$105.40
Purchase #3	$188.95	11.834%	$211.3103	$211.31	$211.30	$211.30
Purchase #4	$178.90	9.790%	$196.4143	$196.41	$196.40	$196.40
Purchase #5	$224.25	4.823%	$235.0656	$235.07	$235.05	$235.10
Purchase #6	$15.35	7.565%	$16.5112	$16.51	$16.50	$16.50
Purchase #7	$111.54	7.856%	$120.3026	$120.30	$120.30	$120.30
7 purchase totals =	$973.32		$1,052.8872	$1,052.88	$1,052.85	$1,052.90