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	$194.86	7.766%	$209.9928	$209.99	$210.00	$210.00
Purchase #2	$162.90	13.492%	$184.8785	$184.88	$184.90	$184.90
Purchase #3	$54.65	9.508%	$59.8461	$59.85	$59.85	$59.80
Purchase #4	$233.74	11.723%	$261.1413	$261.14	$261.15	$261.10
Purchase #5	$244.80	6.264%	$260.1343	$260.13	$260.15	$260.10
Purchase #6	$28.64	9.692%	$31.4158	$31.42	$31.40	$31.40
Purchase #7	$40.73	5.741%	$43.0683	$43.07	$43.05	$43.10
7 purchase totals =	$960.32		$1,050.4771	$1,050.48	$1,050.50	$1,050.40