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	$147.32	10.144%	$162.2641	$162.26	$162.25	$162.30
Purchase #2	$85.67	4.306%	$89.359	$89.36	$89.35	$89.40
Purchase #3	$56.95	9.137%	$62.1535	$62.15	$62.15	$62.20
Purchase #4	$77.69	3.325%	$80.2732	$80.27	$80.25	$80.30
Purchase #5	$36.27	4.689%	$37.9707	$37.97	$37.95	$38.00
Purchase #6	$160.94	8.705%	$174.9498	$174.95	$174.95	$174.90
Purchase #7	$140.29	8.366%	$152.0267	$152.03	$152.05	$152.00
7 purchase totals =	$705.13		$758.9970	$758.99	$758.95	$759.10