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	$249.42	4.825%	$261.4545	$261.45	$261.45	$261.50
Purchase #2	$231.54	3.185%	$238.9145	$238.91	$238.90	$238.90
Purchase #3	$28.92	9.146%	$31.565	$31.57	$31.55	$31.60
Purchase #4	$86.45	11.306%	$96.224	$96.22	$96.20	$96.20
Purchase #5	$125.33	3.756%	$130.0374	$130.04	$130.05	$130.00
Purchase #6	$228.95	13.525%	$259.9155	$259.92	$259.90	$259.90
Purchase #7	$51.55	9.211%	$56.2983	$56.30	$56.30	$56.30
7 purchase totals =	$1,002.16		$1,074.4092	$1,074.41	$1,074.35	$1,074.40