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	$147.69	9.860%	$162.2522	$162.25	$162.25	$162.30
Purchase #2	$152.70	13.800%	$173.7726	$173.77	$173.75	$173.80
Purchase #3	$137.96	11.824%	$154.2724	$154.27	$154.25	$154.30
Purchase #4	$178.73	10.175%	$196.9158	$196.92	$196.90	$196.90
Purchase #5	$76.86	12.148%	$86.197	$86.20	$86.20	$86.20
Purchase #6	$41.30	13.833%	$47.013	$47.01	$47.00	$47.00
Purchase #7	$235.52	4.398%	$245.8782	$245.88	$245.90	$245.90
7 purchase totals =	$970.76		$1,066.3012	$1,066.30	$1,066.25	$1,066.40