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	$91.59	13.463%	$103.9208	$103.92	$103.90	$103.90
Purchase #2	$54.56	4.695%	$57.1216	$57.12	$57.10	$57.10
Purchase #3	$122.60	4.111%	$127.6401	$127.64	$127.65	$127.60
Purchase #4	$164.26	3.443%	$169.9155	$169.92	$169.90	$169.90
Purchase #5	$191.32	4.184%	$199.3248	$199.32	$199.30	$199.30
Purchase #6	$138.74	11.541%	$154.752	$154.75	$154.75	$154.80
Purchase #7	$63.83	5.709%	$67.4741	$67.47	$67.45	$67.50
7 purchase totals =	$826.90		$880.1489	$880.14	$880.05	$880.10