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	$143.33	5.163%	$150.7301	$150.73	$150.75	$150.70
Purchase #2	$43.49	5.540%	$45.8993	$45.90	$45.90	$45.90
Purchase #3	$106.86	8.712%	$116.1696	$116.17	$116.15	$116.20
Purchase #4	$96.96	6.501%	$103.2634	$103.26	$103.25	$103.30
Purchase #5	$132.34	7.279%	$141.973	$141.97	$141.95	$142.00
Purchase #6	$80.86	11.300%	$89.9972	$90.00	$90.00	$90.00
Purchase #7	$84.29	5.348%	$88.7978	$88.80	$88.80	$88.80
7 purchase totals =	$688.13		$736.8304	$736.83	$736.80	$736.90