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	$128.89	12.783%	$145.366	$145.37	$145.35	$145.40
Purchase #2	$180.85	8.805%	$196.7738	$196.77	$196.75	$196.80
Purchase #3	$7.38	3.621%	$7.6472	$7.65	$7.65	$7.60
Purchase #4	$127.28	5.288%	$134.0106	$134.01	$134.00	$134.00
Purchase #5	$104.98	4.606%	$109.8154	$109.82	$109.80	$109.80
Purchase #6	$94.51	12.379%	$106.2094	$106.21	$106.20	$106.20
Purchase #7	$250.89	6.478%	$267.1427	$267.14	$267.15	$267.10
7 purchase totals =	$894.78		$966.9651	$966.97	$966.90	$966.90