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	$47.50	3.204%	$49.0219	$49.02	$49.00	$49.00
Purchase #2	$80.64	13.183%	$91.2708	$91.27	$91.25	$91.30
Purchase #3	$176.29	9.663%	$193.3249	$193.32	$193.30	$193.30
Purchase #4	$118.45	10.670%	$131.0886	$131.09	$131.10	$131.10
Purchase #5	$67.50	10.220%	$74.3985	$74.40	$74.40	$74.40
Purchase #6	$99.49	11.846%	$111.2756	$111.28	$111.30	$111.30
Purchase #7	$63.99	13.531%	$72.6485	$72.65	$72.65	$72.60
7 purchase totals =	$653.86		$723.0288	$723.03	$723.00	$723.00