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	$98.72	4.838%	$103.4961	$103.50	$103.50	$103.50
Purchase #2	$9.51	11.716%	$10.6242	$10.62	$10.60	$10.60
Purchase #3	$58.55	9.690%	$64.2235	$64.22	$64.20	$64.20
Purchase #4	$75.80	3.330%	$78.3241	$78.32	$78.30	$78.30
Purchase #5	$81.48	10.843%	$90.3149	$90.31	$90.30	$90.30
Purchase #6	$193.71	3.186%	$199.8816	$199.88	$199.90	$199.90
Purchase #7	$211.84	10.141%	$233.3227	$233.32	$233.30	$233.30
7 purchase totals =	$729.61		$780.1871	$780.17	$780.10	$780.10