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	$134.29	10.496%	$148.3851	$148.39	$148.40	$148.40
Purchase #2	$159.52	7.397%	$171.3197	$171.32	$171.30	$171.30
Purchase #3	$53.84	11.186%	$59.8625	$59.86	$59.85	$59.90
Purchase #4	$199.31	7.150%	$213.5607	$213.56	$213.55	$213.60
Purchase #5	$106.38	8.874%	$115.8202	$115.82	$115.80	$115.80
Purchase #6	$41.26	8.742%	$44.8669	$44.87	$44.85	$44.90
Purchase #7	$117.91	8.413%	$127.8298	$127.83	$127.85	$127.80
7 purchase totals =	$812.51		$881.6449	$881.65	$881.60	$881.70