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	$55.55	6.152%	$58.9674	$58.97	$58.95	$59.00
Purchase #2	$90.26	10.250%	$99.5117	$99.51	$99.50	$99.50
Purchase #3	$7.56	9.542%	$8.2814	$8.28	$8.30	$8.30
Purchase #4	$224.71	8.414%	$243.6171	$243.62	$243.60	$243.60
Purchase #5	$67.35	6.833%	$71.952	$71.95	$71.95	$72.00
Purchase #6	$160.78	13.503%	$182.4901	$182.49	$182.50	$182.50
Purchase #7	$160.48	6.296%	$170.5838	$170.58	$170.60	$170.60
7 purchase totals =	$766.69		$835.4035	$835.40	$835.40	$835.50