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	$118.87	10.358%	$131.1826	$131.18	$131.20	$131.20
Purchase #2	$168.31	12.596%	$189.5103	$189.51	$189.50	$189.50
Purchase #3	$245.94	11.109%	$273.2615	$273.26	$273.25	$273.30
Purchase #4	$190.78	10.264%	$210.3617	$210.36	$210.35	$210.40
Purchase #5	$91.44	8.415%	$99.1347	$99.13	$99.15	$99.10
Purchase #6	$31.62	12.444%	$35.5548	$35.55	$35.55	$35.60
Purchase #7	$177.96	5.763%	$188.2158	$188.22	$188.20	$188.20
7 purchase totals =	$1,024.92		$1,127.2214	$1,127.21	$1,127.20	$1,127.30