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	$82.69	10.709%	$91.5453	$91.55	$91.55	$91.50
Purchase #2	$181.32	13.501%	$205.8	$205.80	$205.80	$205.80
Purchase #3	$196.94	12.615%	$221.784	$221.78	$221.80	$221.80
Purchase #4	$88.33	13.512%	$100.2651	$100.27	$100.25	$100.30
Purchase #5	$16.90	7.243%	$18.1241	$18.12	$18.10	$18.10
Purchase #6	$232.27	5.607%	$245.2934	$245.29	$245.30	$245.30
Purchase #7	$137.78	11.329%	$153.3891	$153.39	$153.40	$153.40
7 purchase totals =	$936.23		$1,036.2010	$1,036.20	$1,036.20	$1,036.20