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	$111.97	10.334%	$123.541	$123.54	$123.55	$123.50
Purchase #2	$234.88	10.570%	$259.7068	$259.71	$259.70	$259.70
Purchase #3	$85.33	4.676%	$89.32	$89.32	$89.30	$89.30
Purchase #4	$192.35	13.718%	$218.7366	$218.74	$218.75	$218.70
Purchase #5	$222.36	9.481%	$243.442	$243.44	$243.45	$243.40
Purchase #6	$45.36	4.290%	$47.3059	$47.31	$47.30	$47.30
Purchase #7	$195.50	11.146%	$217.2904	$217.29	$217.30	$217.30
7 purchase totals =	$1,087.75		$1,199.3427	$1,199.35	$1,199.35	$1,199.20