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	$164.31	13.240%	$186.0646	$186.06	$186.05	$186.10
Purchase #2	$63.70	10.450%	$70.3567	$70.36	$70.35	$70.40
Purchase #3	$184.47	6.555%	$196.562	$196.56	$196.55	$196.60
Purchase #4	$130.69	13.463%	$148.2848	$148.28	$148.30	$148.30
Purchase #5	$59.53	7.248%	$63.8447	$63.84	$63.85	$63.80
Purchase #6	$106.75	11.779%	$119.3241	$119.32	$119.30	$119.30
Purchase #7	$88.38	3.164%	$91.1763	$91.18	$91.20	$91.20
7 purchase totals =	$797.83		$875.6132	$875.60	$875.60	$875.70