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	$82.78	3.190%	$85.4207	$85.42	$85.40	$85.40
Purchase #2	$196.62	11.864%	$219.947	$219.95	$219.95	$219.90
Purchase #3	$189.28	4.650%	$198.0815	$198.08	$198.10	$198.10
Purchase #4	$94.32	12.707%	$106.3052	$106.31	$106.30	$106.30
Purchase #5	$83.99	9.470%	$91.9439	$91.94	$91.95	$91.90
Purchase #6	$84.47	7.162%	$90.5197	$90.52	$90.50	$90.50
Purchase #7	$243.40	9.464%	$266.4354	$266.44	$266.45	$266.40
7 purchase totals =	$974.86		$1,058.6534	$1,058.66	$1,058.65	$1,058.50