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	$246.93	13.867%	$281.1718	$281.17	$281.15	$281.20
Purchase #2	$218.56	4.178%	$227.6914	$227.69	$227.70	$227.70
Purchase #3	$165.28	8.470%	$179.2792	$179.28	$179.30	$179.30
Purchase #4	$138.59	6.730%	$147.9171	$147.92	$147.90	$147.90
Purchase #5	$6.43	13.641%	$7.3071	$7.31	$7.30	$7.30
Purchase #6	$85.96	10.583%	$95.0571	$95.06	$95.05	$95.10
Purchase #7	$196.89	6.868%	$210.4124	$210.41	$210.40	$210.40
7 purchase totals =	$1,058.64		$1,148.8361	$1,148.84	$1,148.80	$1,148.90