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	$150.92	7.403%	$162.0926	$162.09	$162.10	$162.10
Purchase #2	$94.97	4.365%	$99.1154	$99.12	$99.10	$99.10
Purchase #3	$142.66	11.556%	$159.1458	$159.15	$159.15	$159.10
Purchase #4	$50.52	10.678%	$55.9145	$55.91	$55.90	$55.90
Purchase #5	$93.44	7.320%	$100.2798	$100.28	$100.30	$100.30
Purchase #6	$221.58	5.541%	$233.8577	$233.86	$233.85	$233.90
Purchase #7	$127.43	3.535%	$131.9347	$131.93	$131.95	$131.90
7 purchase totals =	$881.52		$942.3405	$942.34	$942.35	$942.30