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	$225.39	3.769%	$233.8849	$233.88	$233.90	$233.90
Purchase #2	$170.38	12.787%	$192.1665	$192.17	$192.15	$192.20
Purchase #3	$133.57	6.608%	$142.3963	$142.40	$142.40	$142.40
Purchase #4	$148.83	7.169%	$159.4996	$159.50	$159.50	$159.50
Purchase #5	$225.67	7.817%	$243.3106	$243.31	$243.30	$243.30
Purchase #6	$31.36	8.217%	$33.9369	$33.94	$33.95	$33.90
Purchase #7	$110.38	11.467%	$123.0373	$123.04	$123.05	$123.00
7 purchase totals =	$1,045.58		$1,128.2321	$1,128.24	$1,128.25	$1,128.20