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	$243.36	8.815%	$264.8122	$264.81	$264.80	$264.80
Purchase #2	$158.75	4.236%	$165.4747	$165.47	$165.45	$165.50
Purchase #3	$103.47	9.145%	$112.9323	$112.93	$112.95	$112.90
Purchase #4	$50.42	4.258%	$52.5669	$52.57	$52.55	$52.60
Purchase #5	$33.77	12.594%	$38.023	$38.02	$38.00	$38.00
Purchase #6	$123.76	4.478%	$129.302	$129.30	$129.30	$129.30
Purchase #7	$52.27	13.299%	$59.2214	$59.22	$59.20	$59.20
7 purchase totals =	$765.80		$822.3325	$822.32	$822.25	$822.30