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	$164.56	5.213%	$173.1385	$173.14	$173.15	$173.10
Purchase #2	$25.57	6.394%	$27.2049	$27.20	$27.20	$27.20
Purchase #3	$113.32	11.660%	$126.5331	$126.53	$126.55	$126.50
Purchase #4	$28.75	13.381%	$32.597	$32.60	$32.60	$32.60
Purchase #5	$101.55	5.681%	$107.3191	$107.32	$107.30	$107.30
Purchase #6	$199.35	5.476%	$210.2664	$210.27	$210.25	$210.30
Purchase #7	$106.59	4.463%	$111.3471	$111.35	$111.35	$111.30
7 purchase totals =	$739.69		$788.4061	$788.41	$788.40	$788.30