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	$139.90	9.345%	$152.9737	$152.97	$152.95	$153.00
Purchase #2	$189.27	12.545%	$213.0139	$213.01	$213.00	$213.00
Purchase #3	$53.58	10.417%	$59.1614	$59.16	$59.15	$59.20
Purchase #4	$245.84	9.373%	$268.8826	$268.88	$268.90	$268.90
Purchase #5	$175.35	12.361%	$197.025	$197.03	$197.05	$197.00
Purchase #6	$25.60	7.207%	$27.445	$27.45	$27.45	$27.40
Purchase #7	$57.85	3.712%	$59.9974	$60.00	$60.00	$60.00
7 purchase totals =	$887.39		$978.4990	$978.50	$978.50	$978.50