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	$186.57	5.224%	$196.3164	$196.32	$196.30	$196.30
Purchase #2	$178.75	4.797%	$187.3246	$187.32	$187.30	$187.30
Purchase #3	$63.83	9.631%	$69.9775	$69.98	$70.00	$70.00
Purchase #4	$55.55	7.121%	$59.5057	$59.51	$59.50	$59.50
Purchase #5	$179.56	6.494%	$191.2206	$191.22	$191.20	$191.20
Purchase #6	$113.87	9.839%	$125.0737	$125.07	$125.05	$125.10
Purchase #7	$36.28	8.217%	$39.2611	$39.26	$39.25	$39.30
7 purchase totals =	$814.41		$868.6796	$868.68	$868.60	$868.70