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	$204.95	5.226%	$215.6607	$215.66	$215.65	$215.70
Purchase #2	$162.39	10.209%	$178.9684	$178.97	$178.95	$179.00
Purchase #3	$27.41	5.349%	$28.8762	$28.88	$28.90	$28.90
Purchase #4	$194.87	12.828%	$219.8679	$219.87	$219.85	$219.90
Purchase #5	$138.91	9.582%	$152.2204	$152.22	$152.20	$152.20
Purchase #6	$139.72	7.328%	$149.9587	$149.96	$149.95	$150.00
Purchase #7	$90.41	11.501%	$100.8081	$100.81	$100.80	$100.80
7 purchase totals =	$958.66		$1,046.3604	$1,046.37	$1,046.30	$1,046.50