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	$198.83	12.824%	$224.328	$224.33	$224.35	$224.30
Purchase #2	$234.42	13.183%	$265.3236	$265.32	$265.30	$265.30
Purchase #3	$24.29	12.235%	$27.2619	$27.26	$27.25	$27.30
Purchase #4	$194.92	5.475%	$205.5919	$205.59	$205.60	$205.60
Purchase #5	$85.76	6.818%	$91.6071	$91.61	$91.60	$91.60
Purchase #6	$190.31	4.798%	$199.4411	$199.44	$199.45	$199.40
Purchase #7	$77.41	4.148%	$80.621	$80.62	$80.60	$80.60
7 purchase totals =	$1,005.94		$1,094.1746	$1,094.17	$1,094.15	$1,094.10