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	$100.42	5.293%	$105.7352	$105.74	$105.75	$105.70
Purchase #2	$99.30	3.788%	$103.0615	$103.06	$103.05	$103.10
Purchase #3	$176.36	11.386%	$196.4403	$196.44	$196.45	$196.40
Purchase #4	$61.76	8.645%	$67.0992	$67.10	$67.10	$67.10
Purchase #5	$7.99	12.402%	$8.9809	$8.98	$9.00	$9.00
Purchase #6	$244.92	9.355%	$267.8323	$267.83	$267.85	$267.80
Purchase #7	$52.44	13.706%	$59.6274	$59.63	$59.65	$59.60
7 purchase totals =	$743.19		$808.7768	$808.78	$808.85	$808.70