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	$52.74	9.609%	$57.8078	$57.81	$57.80	$57.80
Purchase #2	$41.87	8.576%	$45.4608	$45.46	$45.45	$45.50
Purchase #3	$67.92	7.457%	$72.9848	$72.98	$73.00	$73.00
Purchase #4	$58.54	5.141%	$61.5495	$61.55	$61.55	$61.50
Purchase #5	$153.71	7.525%	$165.2767	$165.28	$165.30	$165.30
Purchase #6	$133.64	6.453%	$142.2638	$142.26	$142.25	$142.30
Purchase #7	$175.25	8.349%	$189.8816	$189.88	$189.90	$189.90
7 purchase totals =	$683.67		$735.2250	$735.22	$735.25	$735.30