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	$13.54	4.573%	$14.1592	$14.16	$14.15	$14.20
Purchase #2	$18.88	10.529%	$20.8679	$20.87	$20.85	$20.90
Purchase #3	$52.28	3.571%	$54.1469	$54.15	$54.15	$54.10
Purchase #4	$176.76	3.678%	$183.2612	$183.26	$183.25	$183.30
Purchase #5	$51.31	12.148%	$57.5431	$57.54	$57.55	$57.50
Purchase #6	$172.32	7.438%	$185.1372	$185.14	$185.15	$185.10
Purchase #7	$40.76	12.361%	$45.7983	$45.80	$45.80	$45.80
7 purchase totals =	$525.85		$560.9138	$560.92	$560.90	$560.90