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	$88.38	9.177%	$96.4906	$96.49	$96.50	$96.50
Purchase #2	$175.68	11.586%	$196.0343	$196.03	$196.05	$196.00
Purchase #3	$193.29	13.376%	$219.1445	$219.14	$219.15	$219.10
Purchase #4	$129.83	8.774%	$141.2213	$141.22	$141.20	$141.20
Purchase #5	$29.38	10.465%	$32.4546	$32.45	$32.45	$32.50
Purchase #6	$95.89	5.247%	$100.9213	$100.92	$100.90	$100.90
Purchase #7	$247.88	7.152%	$265.6084	$265.61	$265.60	$265.60
7 purchase totals =	$960.33		$1,051.8750	$1,051.86	$1,051.85	$1,051.80