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	$214.35	3.288%	$221.3978	$221.40	$221.40	$221.40
Purchase #2	$99.73	9.658%	$109.3619	$109.36	$109.35	$109.40
Purchase #3	$222.81	4.660%	$233.1929	$233.19	$233.20	$233.20
Purchase #4	$117.99	9.233%	$128.884	$128.88	$128.90	$128.90
Purchase #5	$104.85	12.797%	$118.2677	$118.27	$118.25	$118.30
Purchase #6	$219.86	9.543%	$240.8412	$240.84	$240.85	$240.80
Purchase #7	$26.94	9.294%	$29.4438	$29.44	$29.45	$29.40
7 purchase totals =	$1,006.53		$1,081.3893	$1,081.38	$1,081.40	$1,081.40