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	$155.42	4.632%	$162.6191	$162.62	$162.60	$162.60
Purchase #2	$73.79	4.357%	$77.005	$77.01	$77.00	$77.00
Purchase #3	$11.35	10.367%	$12.5267	$12.53	$12.55	$12.50
Purchase #4	$130.48	11.250%	$145.159	$145.16	$145.15	$145.20
Purchase #5	$86.98	12.148%	$97.5463	$97.55	$97.55	$97.50
Purchase #6	$80.36	11.280%	$89.4246	$89.42	$89.40	$89.40
Purchase #7	$151.26	6.403%	$160.9452	$160.95	$160.95	$160.90
7 purchase totals =	$689.64		$745.2259	$745.24	$745.20	$745.10