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	$194.97	9.371%	$213.2406	$213.24	$213.25	$213.20
Purchase #2	$57.83	6.440%	$61.5543	$61.55	$61.55	$61.60
Purchase #3	$153.38	10.819%	$169.9742	$169.97	$169.95	$170.00
Purchase #4	$50.47	9.748%	$55.3898	$55.39	$55.40	$55.40
Purchase #5	$20.27	6.694%	$21.6269	$21.63	$21.65	$21.60
Purchase #6	$98.94	4.375%	$103.2686	$103.27	$103.25	$103.30
Purchase #7	$129.52	11.851%	$144.8694	$144.87	$144.85	$144.90
7 purchase totals =	$705.38		$769.9238	$769.92	$769.90	$770.00