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	$221.95	3.707%	$230.1777	$230.18	$230.20	$230.20
Purchase #2	$25.76	6.852%	$27.5251	$27.53	$27.55	$27.50
Purchase #3	$111.53	9.331%	$121.9369	$121.94	$121.95	$121.90
Purchase #4	$116.56	9.297%	$127.3966	$127.40	$127.40	$127.40
Purchase #5	$31.27	6.108%	$33.18	$33.18	$33.20	$33.20
Purchase #6	$125.77	4.628%	$131.5906	$131.59	$131.60	$131.60
Purchase #7	$40.60	3.596%	$42.06	$42.06	$42.05	$42.10
7 purchase totals =	$673.44		$713.8669	$713.88	$713.95	$713.90