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	$212.34	13.516%	$241.0399	$241.04	$241.05	$241.00
Purchase #2	$172.87	3.534%	$178.9792	$178.98	$179.00	$179.00
Purchase #3	$90.86	9.610%	$99.5916	$99.59	$99.60	$99.60
Purchase #4	$112.79	6.669%	$120.312	$120.31	$120.30	$120.30
Purchase #5	$152.78	7.369%	$164.0384	$164.04	$164.05	$164.00
Purchase #6	$176.93	3.596%	$183.2924	$183.29	$183.30	$183.30
Purchase #7	$176.28	4.370%	$183.9834	$183.98	$184.00	$184.00
7 purchase totals =	$1,094.85		$1,171.2369	$1,171.23	$1,171.30	$1,171.20