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	$148.66	5.645%	$157.0519	$157.05	$157.05	$157.10
Purchase #2	$75.56	8.692%	$82.1277	$82.13	$82.15	$82.10
Purchase #3	$163.95	11.553%	$182.8911	$182.89	$182.90	$182.90
Purchase #4	$33.94	3.437%	$35.1065	$35.11	$35.10	$35.10
Purchase #5	$172.31	9.652%	$188.9414	$188.94	$188.95	$188.90
Purchase #6	$93.81	6.466%	$99.8758	$99.88	$99.90	$99.90
Purchase #7	$234.61	12.571%	$264.1028	$264.10	$264.10	$264.10
7 purchase totals =	$922.84		$1,010.0972	$1,010.10	$1,010.15	$1,010.10