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	$33.69	3.731%	$34.947	$34.95	$34.95	$34.90
Purchase #2	$72.40	8.225%	$78.3549	$78.35	$78.35	$78.40
Purchase #3	$127.73	9.269%	$139.5693	$139.57	$139.55	$139.60
Purchase #4	$116.37	10.121%	$128.1478	$128.15	$128.15	$128.10
Purchase #5	$219.76	6.216%	$233.4203	$233.42	$233.40	$233.40
Purchase #6	$184.61	13.835%	$210.1508	$210.15	$210.15	$210.20
Purchase #7	$5.74	9.432%	$6.2814	$6.28	$6.30	$6.30
7 purchase totals =	$760.30		$830.8715	$830.87	$830.85	$830.90