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	$229.28	10.356%	$253.0242	$253.02	$253.00	$253.00
Purchase #2	$128.71	9.777%	$141.294	$141.29	$141.30	$141.30
Purchase #3	$95.92	7.834%	$103.4344	$103.43	$103.45	$103.40
Purchase #4	$245.61	3.470%	$254.1327	$254.13	$254.15	$254.10
Purchase #5	$140.41	10.781%	$155.5476	$155.55	$155.55	$155.50
Purchase #6	$109.31	7.230%	$117.2131	$117.21	$117.20	$117.20
Purchase #7	$147.81	11.210%	$164.3795	$164.38	$164.40	$164.40
7 purchase totals =	$1,097.05		$1,189.0255	$1,189.01	$1,189.05	$1,188.90