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	$96.91	13.487%	$109.9803	$109.98	$110.00	$110.00
Purchase #2	$45.32	4.223%	$47.2339	$47.23	$47.25	$47.20
Purchase #3	$54.35	8.794%	$59.1295	$59.13	$59.15	$59.10
Purchase #4	$168.73	3.547%	$174.7149	$174.71	$174.70	$174.70
Purchase #5	$71.46	10.441%	$78.9211	$78.92	$78.90	$78.90
Purchase #6	$33.66	10.411%	$37.1643	$37.16	$37.15	$37.20
Purchase #7	$52.79	13.603%	$59.971	$59.97	$59.95	$60.00
7 purchase totals =	$523.22		$567.1150	$567.10	$567.10	$567.10