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	$53.97	8.483%	$58.5483	$58.55	$58.55	$58.50
Purchase #2	$205.90	4.549%	$215.2664	$215.27	$215.25	$215.30
Purchase #3	$140.52	12.440%	$158.0007	$158.00	$158.00	$158.00
Purchase #4	$67.43	12.531%	$75.8797	$75.88	$75.90	$75.90
Purchase #5	$7.44	4.672%	$7.7876	$7.79	$7.80	$7.80
Purchase #6	$56.41	5.129%	$59.3033	$59.30	$59.30	$59.30
Purchase #7	$31.89	13.289%	$36.1279	$36.13	$36.15	$36.10
7 purchase totals =	$563.56		$610.9139	$610.92	$610.95	$610.90