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	$55.53	9.767%	$60.9536	$60.95	$60.95	$61.00
Purchase #2	$32.28	9.605%	$35.3805	$35.38	$35.40	$35.40
Purchase #3	$18.50	9.382%	$20.2357	$20.24	$20.25	$20.20
Purchase #4	$98.36	9.110%	$107.3206	$107.32	$107.30	$107.30
Purchase #5	$37.86	3.280%	$39.1018	$39.10	$39.10	$39.10
Purchase #6	$228.38	4.333%	$238.2757	$238.28	$238.30	$238.30
Purchase #7	$81.75	12.404%	$91.8903	$91.89	$91.90	$91.90
7 purchase totals =	$552.66		$593.1582	$593.16	$593.20	$593.20