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	$130.25	9.297%	$142.3593	$142.36	$142.35	$142.40
Purchase #2	$151.75	12.561%	$170.8113	$170.81	$170.80	$170.80
Purchase #3	$64.36	6.171%	$68.3317	$68.33	$68.35	$68.30
Purchase #4	$85.66	4.297%	$89.3408	$89.34	$89.35	$89.30
Purchase #5	$205.30	8.286%	$222.3112	$222.31	$222.30	$222.30
Purchase #6	$249.66	7.699%	$268.8813	$268.88	$268.90	$268.90
Purchase #7	$161.70	6.715%	$172.5582	$172.56	$172.55	$172.60
7 purchase totals =	$1,048.68		$1,134.5938	$1,134.59	$1,134.60	$1,134.60