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	$189.90	3.394%	$196.3452	$196.35	$196.35	$196.30
Purchase #2	$35.49	7.394%	$38.1141	$38.11	$38.10	$38.10
Purchase #3	$86.97	10.339%	$95.9618	$95.96	$95.95	$96.00
Purchase #4	$170.32	6.268%	$180.9957	$181.00	$181.00	$181.00
Purchase #5	$145.98	13.380%	$165.5121	$165.51	$165.50	$165.50
Purchase #6	$187.38	6.357%	$199.2917	$199.29	$199.30	$199.30
Purchase #7	$48.78	4.299%	$50.8771	$50.88	$50.90	$50.90
7 purchase totals =	$864.82		$927.0977	$927.10	$927.10	$927.10